An intercomparison of a curve fitting and least squares approach is presented for the estimation of CHL, CDOM and TSM for two inland waters. In the inversion procedures two different bio-optical models were used, i.e. the Gordon model and the model of Albert and Mobley. The intercomparison is based on simulated APEX reflectance data. For these simulations two field campaigns were organised on the Scheldt river and Lake Constance to collect water samples. They were analysed for the optical properties and concentration values of the three optically active constituents. Reflectance data were then simulated using Hydrolight and the models of Gordon and Albert and Mobley. These simulations were used to test several inversion approaches. The curve fitting with the model of Albert and Mobley provided the best results for the Scheldt river. For Lake Constance no single procedure outperformed the others.