This paper examines the influence of charge carrier diffusion on photoenhanced current characteristics. The results of our analysis indicates that in the case of thin layers the diffusion of charge carriers leads to the following type of photoenhanced current-voltage relationship: j similar to U-n with 1 less than or equal to n < 2. Experimental results of photoenhanced current obtained on tetracene and pentacene layers confirming the role of charge carrier diffusion in thin samples are presented.