This study compared the efficacy of two electrotherapy modalities for pain treatment in rehabilitation programs of patellofernoral pain syndrome. In a prospective randomized study, 16 patients (23 affected knees) were treated with TENS and 14 patients (19 affected knees) were treated for the same period with diadynamic current (DDC). Subjective pain, knee function, and activity level of the patients were measured before and after the treatment. Subjective pain and functional levels were assessed by visual analogue scale, the Lysholm Knee Scoring Scale and Squat Testing for 30 seconds. To assess their activity level a 4-Level Activity Test was used. All the parameters in each group showed significant improvements after 12 weeks of physical therapy (p < 0.05). Statistical analyses demonstrated that there were no significant differencess between the groups in pain relief, improvements in knee functions and activity level after the treatments, although DDC seemed to have slightly better pain modulation effect than TENS. In conclusion, both analgesic modalities can be used for pain relief in rehabilitation programs of the patellofemoral pain syndrome.