For　the　first　time,　a　systematical　investigation　has　been　carried　out　to　verify　luminescent　molybdenum　disulfide　quantum　dots　(MoS2　QDs).　We　found　that　the　well-reported　blue　fluorescence　of　the　so-called　＂MoS2　QDs＂　is　mainly　originated　from　the　co-present　carbon　based　dots　rather　than　MoS2.　Furthermore,　the　band　gap　of　MoS2　is　independent　of　the　lateral　size,　and　it　is　impossible　to　obtain　luminescent　MoS2　QDs　by　reducing　the　lateral　size.