Phenolic compounds from leaves of lingonberry ( Vaccinium vitis-idaea L.), bilberry ( Vaccinium myrtillus L.), and the natural hybrid of bilberry and lingonberry ( Vaccinium x intermedium Ruthe L., hybrid bilberry) were identified using LC/TOF-MS and LC/MS/MS after extraction from the plant material in methanol in an ultrasonicator. The phenolic profiles in the plants were compared using the LC/TOF-MS responses. This is the first thorough report of phenolic compounds in hybrid bilberry. In total, 51 different phenolic compounds were identified, including flavan-3-ols, proanthocyanidins, flavonols and their glycosides, and various phenolic acid conjugates. Of the identified compounds, 35 were detected in bilberry, 36 in lingonberry, and 46 in the hybrid. To our knowledge, seven compounds were previously unreported in Vaccinium genus and many of the compounds are reported for the first time from bilberry and lingonberry.