Aim of the study: To evaluate clinical effectiveness of two different light doses when treating actinic keratoses with photodynamic therapy with 20% 5-aminolevulinic acid.

To determine and compare clinical and histological effectiveness of different (70 J/cm2 ir 100 J/cm2) light doses when treating actinic keratoses with photodynamic therapy.

To determine pain intensity during photodynamic therapy with visual analogue scale and factors influencing pain during the procedure.

Inclusion Criteria:

1. Male or female subject older than 50 years.
2. Subject has to read Patient Information Sheet and read and sign the Informed Consent form prior to any study related procedure.
3. AK with the largest diameter ≤3 cm (measuring the longest axis).
4. 2 or more AK with symmetrical distribution on the face or scalp.
5. Clinically and histologically confirmed AK of grade I or II.
6. Subject must be willing and capable of cooperating to the extent and degree required by the protocol.
7. Patient is not the subject of the administrative or legal judicial proceeding.
8. Subject has social health security required by laws of health care institutions.

Exclusion Criteria:

1. Patients with more than 5 AK in the planned treatment area.
2. A recurrent AK: AK that has been previously treated in the study area.
3. Very hyperkeratotic, grade 3 (on a 0-3 scale) AK lesions among the target lesions.
4. AK located on the nose.
5. Other skin lesions (diseases) in the tumor study area.
6. Subject with known hereditary basal cell carcinoma syndromes (Gorlin-Goltz, Basex-Dupre-Christol et al.).
7. Subject with a history of cutaneous photosensitization or porphyria or Xeroderma pigmentosum, hypersensitivity to porphyrins, or photodermatosis.
8. Subject who had received photosensitizing drugs 30 days before study start.
9. Subjects who had received immunomodulatory or immunosuppressive therapies, including systemic and topical steroids, imiquimod or solaraze, interferon and acitretin 6 months prior to study treatment initiation.
10. Subject who had participated in another investigational drug or device research study within 30 days of enrolment.
11. Subject had received in the study area laser resurfacing, chemical peels, topical application fluorouracil or other drugs for the treatment of AKs within 2 months before study entry.
12. Subject with known hypersensitivity to 5-aminolevulinc acid, a similar compound or excipients of the cream.
13. Subject with known status after organ transplantation.