As a test of the conjectured QCD/supergravity duality, we consider mass gaps in the supergravity construction of QCD 2. We find a mass gap in the dual field theory both when using non-rotating and rotating black D2-branes as backgrounds in the supergravity construction of QCD 2. So, since pure QCD 2 does not have a mass gap, the dual field theory of the supergravity construction of QCD 2 cannot be pure QCD 2. Considering the mass scales in the dual field theory of the supergravity construction of QCD 2, we find that this is explainable both in the case of the non-rotating background and of the rotating background. In particular, the mass gap in the case of the rotating background can be explained using results of the large angular momentum limit of euclidean rotating branes, obtained recently by Cvetic and Gubser. We furthermore remark on the possible implications for the mass gaps in the supergravity constructions of QCD 3 and QCD 4.