Drain the canned cherries; place liquid in medium saucepan and set cherries aside.
In a small mixing bowl, combine cornstarch and cold water; mix well. Whisk cornstarch into cherry liquid. Heat to boiling point and boil for 5 minutes, stirring constantly.
Add sugar and lemon juice. Stir and remove from heat and chill. When this syrup is cool, blend in the sour cream and add the drained cherries. Chill well and serve in chilled cups.
