This study aims to compare effectiveness of different densities of carbon dioxide fractional laser in the treatment of postburn scar.

The study included 25 Egyptian patients with burn scars recruited from the Out Patient Clinic, Dermatology Department, Cairo University. Each has three post burn scars, assigned to monthly fractional Carbon dioxide laser sessions with a total of 3 sessions. parameters are :

Lesion A or part A parameters: 20 W, 800-1000μs dwell time, 2 to 3 stacks according to scar thickness, 900µm spacing (7.4% density).

Lesion B or part B parameters: 20 W, 800-1000μs dwell time, 2 to 3 stacks according to scar thickness, 600µm spacing (12.6% density).

Lesion C or part C parameters: 20 W, 800-1000μs dwell time, 2 to 3 stacks according to scar thickness, 300 µm spacing (25.6% density).

3 mm punch biopsy is taken before and one month after last session for assessment of collagen via (Masson's trichrome strain). In addition clinical evaluation is done via Vancouver & Patient and Observer Scar Assessment Scale .

Inclusion Criteria:

• • Burn scars of at least 1 year duration.

  • Patients with three separate lesions each of them about 2 to 5cm or patients with single lesion equal or more than 8 to 10cm.

Exclusion Criteria:

• • Pregnancy.

  • Lactation.
  • Oral retinoid drugs within the past 6 months.

masked to the parameters of laser treatment in each lesion