Objective. Systemic corticosteroids are the mainstay treatment for PV oral lesions; the aim of this study is to evaluate the efficacy of PBMT with a 645 nm diode laser as a supportive topical therapy in patients with PV induced erosive-ulcerative oral lesions. Materials and Methods. This double-blind placebo-controlled study divided patients into two groups: A, patients receiving laser therapy (Raffaello 980 Bio, Dental Medical Technologies, Italy with the following parameters: 100 mW power, 645 nm wave length, irradiation area 1 cm2, application time 30 sec/cm2, energy density 3 J/cm2, scanning modality) and B, receiving sham therapy (placebo). All patients were being treated also with a systemic corticosteroid therapy i.e. prednisone 0.5 mg/Kg per day. Size of lesions, VAS and satisfaction were evaluated before the treatment (T0), after 4 weeks (T1) and after 8 weeks as a follow-up (T2). Results. A total of 50 lesions were evaluated. About lesions size, there was a statistical significative difference between the two groups just at T2 (p=0.0193), though VAS significantly decreased both at T1 (p=0.0198) and at T2 (p=0.0087). In general, all patients were satisfied of the treatment received. Conclusion. PBMT can be considered a validate supportive therapeutic option, even if further RCTs studies with wide sample sizes and standardized management protocols are suggested