A vapor chamber with integrated hollow fins was manufactured and tested, with the aim of identifying the optimal fin geometry to prevent liquid hold-up and flooding at the condenser. In particular, the influence of the transverse cross section was experimentally investigated. Circular, triangular and fluted cross sections were compared, with inscribed diameters ranging from 1.3 to 2.6 mm. The air-cooled fins were made of polymer in order to visualize the condensation regimes. When operating with HFE-7100, three regimes were identified with increasing heat load (up to 95 W): filmwise condensation, plug condensation and flooding, which significantly deteriorates the heat transfer performance. The triangular cross section is the most interesting shape among those tested because flooding occurs at higher heat load and/or smaller diameter than in other shapes thanks to drainage into the corners. Circular fins have the worst performance and fluted ones are in-between. The critical diameter below which flooding occurs even at low heat load is around 2.0 mm for a triangular section and 2.5 mm for a circular one. Consequently, with an optimum fin placement, the total convective surface area at the condenser could be increased by about 15% when using triangles instead of circles.