Abstract Background Recent years have seen an increase in the off-label use of photodynamic therapy for the treatment of a variety of skin diseases. Plaque-phase mycosis fungoides is among the most promising possibilities for the use of this treatment. Objectives To evaluate the treatment of plaque-phase mycosis fungoides with photodynamic therapy and compare the results obtained using fluorescence photography. Material and methods We performed a prospective, descriptive, observational study. Twelve patients with 24 lesions were treated with topical methyl aminolevulinate (MAL) under an occlusive dressing for 3 hours, followed by 8 minutes of red light (630 nm, 37 J/ cm 2; Aktilite). Results Six patients had a complete response, 5 a partial response, and 1 did not respond to treatment. A mean of 5.7 sessions was applied and no side effects were reported. Treatment tolerance was excellent. Conclusions Photodynamic therapy with MAL appears to be a good treatment option for patients with plaque-phase mycosis fungoides with a small number of lesions.