Stopping powers of 1.0 - 2.6 MeV protons in Mylar, Makrofol and Cellulose nitrate were measured. The results have been compared with scanty experimental data in the literature and with calculated values obtained by using the TRIM 92 computer code. These values agree well with each other within uncertainties. In the case of Mylar and LR 115, maximum deviations of 9.5% and 4.5% from the semi-emperical curves were observed. In the case of Makrofol foils, a maximum deviation of 3% was found. Considering the accuracy of theories this discrepancy is not that significant.