diff --git a/src/vs/workbench/api/browser/mainThreadComments.ts b/src/vs/workbench/api/browser/mainThreadComments.ts
index 0ecd0d8a195..29f7b613e5a 100644
--- a/src/vs/workbench/api/browser/mainThreadComments.ts
+++ b/src/vs/workbench/api/browser/mainThreadComments.ts
@@ -486,6 +486,7 @@ export class MainThreadComments extends Disposable implements MainThreadComments
 	) {
 		super();
 		this._proxy = extHostContext.getProxy(ExtHostContext.ExtHostComments);
+		this._commentService.unregisterCommentController();
 
 		this._register(this._commentService.onDidChangeActiveCommentThread(async thread => {
 			const handle = (thread as MainThreadCommentThread<IRange | ICellRange>).controllerHandle;
diff --git a/src/vs/workbench/api/common/extHostComments.ts b/src/vs/workbench/api/common/extHostComments.ts
index 13f02e08b35..c44e10e1acc 100644
--- a/src/vs/workbench/api/common/extHostComments.ts
+++ b/src/vs/workbench/api/common/extHostComments.ts
@@ -7,7 +7,7 @@ import { asPromise } from 'vs/base/common/async';
 import { CancellationToken } from 'vs/base/common/cancellation';
 import { debounce } from 'vs/base/common/decorators';
 import { Emitter } from 'vs/base/common/event';
-import { DisposableStore, IDisposable, MutableDisposable } from 'vs/base/common/lifecycle';
+import { DisposableStore, MutableDisposable } from 'vs/base/common/lifecycle';
 import { MarshalledId } from 'vs/base/common/marshallingIds';
 import { URI, UriComponents } from 'vs/base/common/uri';
 import { IRange } from 'vs/editor/common/core/range';
@@ -31,7 +31,7 @@ interface ExtHostComments {
 export function createExtHostComments(mainContext: IMainContext, commands: ExtHostCommands, documents: ExtHostDocuments): ExtHostCommentsShape & ExtHostComments {
 	const proxy = mainContext.getProxy(MainContext.MainThreadComments);
 
-	class ExtHostCommentsImpl implements ExtHostCommentsShape, ExtHostComments, IDisposable {
+	class ExtHostCommentsImpl implements ExtHostCommentsShape, ExtHostComments {
 
 		private static handlePool = 0;
 
@@ -244,9 +244,6 @@ export function createExtHostComments(mainContext: IMainContext, commands: ExtHo
 				return Promise.resolve(undefined);
 			});
 		}
-		dispose() {
-
-		}
 	}
 	type CommentThreadModification = Partial<{
 		range: vscode.Range;
diff --git a/src/vs/workbench/contrib/comments/browser/commentService.ts b/src/vs/workbench/contrib/comments/browser/commentService.ts
index 5dc5ddf30e6..6a8cc9c290c 100644
--- a/src/vs/workbench/contrib/comments/browser/commentService.ts
+++ b/src/vs/workbench/contrib/comments/browser/commentService.ts
@@ -80,14 +80,14 @@ export interface ICommentService {
 	readonly onDidUpdateCommentingRanges: Event<{ owner: string }>;
 	readonly onDidChangeActiveCommentingRange: Event<{ range: Range; commentingRangesInfo: CommentingRanges }>;
 	readonly onDidSetDataProvider: Event<void>;
-	readonly onDidDeleteDataProvider: Event<string>;
+	readonly onDidDeleteDataProvider: Event<string | undefined>;
 	readonly onDidChangeCommentingEnabled: Event<boolean>;
 	readonly isCommentingEnabled: boolean;
 	setDocumentComments(resource: URI, commentInfos: ICommentInfo[]): void;
 	setWorkspaceComments(owner: string, commentsByResource: CommentThread<IRange | ICellRange>[]): void;
 	removeWorkspaceComments(owner: string): void;
 	registerCommentController(owner: string, commentControl: ICommentController): void;
-	unregisterCommentController(owner: string): void;
+	unregisterCommentController(owner?: string): void;
 	getCommentController(owner: string): ICommentController | undefined;
 	createCommentThreadTemplate(owner: string, resource: URI, range: Range | undefined): void;
 	updateCommentThreadTemplate(owner: string, threadHandle: number, range: Range): Promise<void>;
@@ -111,8 +111,8 @@ export class CommentService extends Disposable implements ICommentService {
 	private readonly _onDidSetDataProvider: Emitter<void> = this._register(new Emitter<void>());
 	readonly onDidSetDataProvider: Event<void> = this._onDidSetDataProvider.event;
 
-	private readonly _onDidDeleteDataProvider: Emitter<string> = this._register(new Emitter<string>());
-	readonly onDidDeleteDataProvider: Event<string> = this._onDidDeleteDataProvider.event;
+	private readonly _onDidDeleteDataProvider: Emitter<string | undefined> = this._register(new Emitter<string | undefined>());
+	readonly onDidDeleteDataProvider: Event<string | undefined> = this._onDidDeleteDataProvider.event;
 
 	private readonly _onDidSetResourceCommentInfos: Emitter<IResourceCommentThreadEvent> = this._register(new Emitter<IResourceCommentThreadEvent>());
 	readonly onDidSetResourceCommentInfos: Event<IResourceCommentThreadEvent> = this._onDidSetResourceCommentInfos.event;
@@ -239,8 +239,12 @@ export class CommentService extends Disposable implements ICommentService {
 		this._onDidSetDataProvider.fire();
 	}
 
-	unregisterCommentController(owner: string): void {
-		this._commentControls.delete(owner);
+	unregisterCommentController(owner?: string): void {
+		if (owner) {
+			this._commentControls.delete(owner);
+		} else {
+			this._commentControls.clear();
+		}
 		this._onDidDeleteDataProvider.fire(owner);
 	}
 
diff --git a/src/vs/workbench/contrib/comments/browser/commentsController.ts b/src/vs/workbench/contrib/comments/browser/commentsController.ts
index fab32d698f1..53fa7b55c35 100644
--- a/src/vs/workbench/contrib/comments/browser/commentsController.ts
+++ b/src/vs/workbench/contrib/comments/browser/commentsController.ts
@@ -353,8 +353,13 @@ export class CommentController implements IEditorContribution {
 		this.globalToDispose.add(this._commentThreadRangeDecorator = new CommentThreadRangeDecorator(this.commentService));
 
 		this.globalToDispose.add(this.commentService.onDidDeleteDataProvider(ownerId => {
-			delete this._pendingNewCommentCache[ownerId];
-			delete this._pendingEditsCache[ownerId];
+			if (ownerId) {
+				delete this._pendingNewCommentCache[ownerId];
+				delete this._pendingEditsCache[ownerId];
+			} else {
+				this._pendingNewCommentCache = {};
+				this._pendingEditsCache = {};
+			}
 			this.beginCompute();
 		}));
 		this.globalToDispose.add(this.commentService.onDidSetDataProvider(_ => this.beginCompute()));
diff --git a/src/vs/workbench/contrib/comments/browser/commentsView.ts b/src/vs/workbench/contrib/comments/browser/commentsView.ts
index 5a787f30cc0..c04e4bfb30e 100644
--- a/src/vs/workbench/contrib/comments/browser/commentsView.ts
+++ b/src/vs/workbench/contrib/comments/browser/commentsView.ts
@@ -191,6 +191,7 @@ export class CommentsPanel extends FilterViewPane implements ICommentsView {
 
 		this._register(this.commentService.onDidSetAllCommentThreads(this.onAllCommentsChanged, this));
 		this._register(this.commentService.onDidUpdateCommentThreads(this.onCommentsUpdated, this));
+		this._register(this.commentService.onDidDeleteDataProvider(this.onDataProviderDeleted, this));
 
 		const styleElement = dom.createStyleSheet(container);
 		this.applyStyles(styleElement);
@@ -470,6 +471,14 @@ export class CommentsPanel extends FilterViewPane implements ICommentsView {
 		}
 	}
 
+	private onDataProviderDeleted(owner: string | undefined): void {
+		this.cachedFilterStats = undefined;
+		this.commentsModel.deleteCommentsByOwner(owner);
+
+		this.totalComments = 0;
+		this.refresh();
+	}
+
 	private updateSomeCommentsExpanded() {
 		this.someCommentsExpandedContextKey.set(this.isSomeCommentsExpanded());
 	}
diff --git a/src/vs/workbench/contrib/comments/common/commentModel.ts b/src/vs/workbench/contrib/comments/common/commentModel.ts
index 7f842927670..5ee5ab1f657 100644
--- a/src/vs/workbench/contrib/comments/common/commentModel.ts
+++ b/src/vs/workbench/contrib/comments/common/commentModel.ts
@@ -85,6 +85,15 @@ export class CommentsModel {
 		this.updateResourceCommentThreads();
 	}
 
+	public deleteCommentsByOwner(owner?: string): void {
+		if (owner) {
+			this.commentThreadsMap.set(owner, []);
+		} else {
+			this.commentThreadsMap.clear();
+		}
+		this.updateResourceCommentThreads();
+	}
+
 	public updateCommentThreads(event: ICommentThreadChangedEvent): boolean {
 		const { owner, removed, changed, added } = event;