We investigated two-dimensional electron- (2DES) and hole systems (2DHS) in the fractional quantum Hall regime for filling factors ν=1/3 and ν=2/3. Due to a metallic top gate we are able to vary the electron-/hole density of the samples over a wide range. Measuring activated transport on these systems with perpendicular magnetic fields up to 18 T and temperatures down to about 30 mK allows to get an insight into the excitation spectra. Although the bandstructure of holes is complicated compared to those of electrons, the theoretical description of the fractional quantum Hall effect in the composite Fermion picture should hold for both types of particles. We analyzed and compared the results for the different filling factors and systems.