Our aim is to investigate a relationship between trichogram findings and demographic/ clinical features in psoriasis and seborrheic dermatitis patients. Trichogram method may be instructive in differentiation of these two diseases and may reduce the necessity of biopsy in presence of specific trichogram findings. Material and Methods: Thirty one psoriasis and 26 seborrheic dermatitis patients and 21 healthy controls were included in the study. Hairs were counted and classified as anagen, telogen, catagen and dysplastic hair. Results: In psoriasis and seborrheic dermatitis patients, a statistically significant increase was determined in telogen and dysplastic hair rates both in the areas with or without lesions comparing to healthy control group. Whereas no significant difference in terms of catagen hair rate was determined in all three groups. Anagen hair rates were significantly decreased in psoriasis and seborrheic dermatitis patient groups comparing to control group. When trichogram findings of psoriasis patients' areas with and without lesion; in areas with lesion, an increase was determined in dysplastic and telogen hair rate and a decrease was determined in catagen and anagen hair rates comparing to areas without lesion. These differences were statistically significant. When trichogram findings of seborrheic dermatitis patients' areas with and without lesion; in areas with lesion an increase was determined in dysplastic hair rate, a decrease was determined in anagen hair rate. While these differences were found statistically significant, no significant difference was found in catagen and telogen hair rates. Conclusion: In psoriasis and seborrheic dermatitis patients' scalp involvement, increased telogen and dysplastic hair rates and decreased anagen hair rates are seen in terms of trichogram findings comparing to healthy control groups. There was no statistically significant difference between psoriasis and seborrheic dermatitis. As a result of this study psoriasis and seborrheic dermatitis cause a decrease in the anagen/ telogen rate and both increase the dysplastic hair count.