INTRODUCTION: Daylight PDT (DLPDT) is a new PDT procedure. Several trials demonstrate that DLPDT achieves similar response rates with conventional PDT (CPDT) in the treatment of non-hyperkeratotic actinic keratoses (AKs) in a nearly painless way. It seems that DLPDT represents a more convenient and equally effective treatment modality. Data on long-term efficacy of DLPDT are limited.OBJECTIVE: To compare short- and long-term efficacy, safety and tolerability of DLPDT with that of CPDT in face and scalp AKs.METHODS: The study, an intra-individual right-left comparison study, was conducted in three centres in North, Center and South Greece. Eligible patients received either DLPDT or CPDT randomly allocated to alternate sides of face or scalp. Patients were evaluated at baseline, 3 and 12 months after treatment. Assessments included lesion response at 3 and 12 months, PDT-associated pain during PDT session, local skin reactions 3 days after treatment as well as patients' preference 3 months after treatment.RESULTS: A total of 46 patients completed the study. Three months after treatment, the overall lesion complete response rate was 78% for DLPDT and 80.6% for CPDT. At the 12-month follow-up, response rate decreased to 71.8% and 73.7% for DLPDT and CPDT accordingly. Regarding response based on lesion grade, response rates obtained in grade-I lesions were higher with DLPDT, while treatment with CPDT resulted to higher rates of cured grade-II lesions at both follow-up visits. Results were not supported by statistical significance. DLPDT was associated with significantly lower pain and reduced severity of local skin reactions. Patients' preference favoured DLPDT.CONCLUSIONS: Our study demonstrated that DLPDT is similar to CPDT in terms of long-term efficacy and recurrence rates in the treatment of face and scalp AKs. DLPDT demonstrated a better tolerability profile as it was associated with lower pain and less severe adverse events.