BACKGROUND The optimal parameters of low level laser therapy (LLLT) are still under debate. It has been documented that a dose or 5 J/cm2 would be capable to accelerate the wound healing process in patients. However, the optimal delivering form, i.e. power intensity, is unknown. Therefore, the aim of our study was to compare different power densities of LLLT. METHODS Sixteen male Sprague-Dawley rats were included in this experiment and randomized into two groups, normal healthy group and streptozotocine induced diabetic group. In general anesthesia four full thickness skin incisions were performed under standard aseptic conditions on the back of each rat and immediately closed using intradermal running suture. Three wounds were stimulated with diode laser (wavelength: 635 nm; daily dose 5 J/cm2; power densities: 1 mW/cm2, 5 mW/cm2 and 15 mW/cm2) each with different power density while the fourth wound served as control. Six days after surgery animals were sacrificed and samples removed for histological evaluation. RESULTS Our study demonstrated that LLLT positively influences wound healing. The most significant changes were observed in wounds stimulated at the highest power density 15 mW/cm2. Since using the highest power density the shortest time is needed to achieve the optimal daily dose of 5 J/cm2, it can be suggested that 15 mW/cm2 might be optimal parameter for such a therapy in patients.