We report on the measurements of electrons trapped in solid molecular films of H2, HD, and D2. A narrow ESR line associated with the trapped electrons was detected with g=2.00233(5)(5, which turned out to be shifted by −0.3 G from the free electron resonance. Comparison is made with earlier measurements where a similar line has been seen. In addition, for a H2:D2D2:H2 mixture, after raising the temperature above 1 K, we observe a strong line at the location of the electron cyclotron resonance. The line amplitude is dependent on temperature and has an activation energy of 26 K. We believe that at elevated temperatures, electrons diffuse from the bulk of the film to the surface.