PurposeTreatment non-adherence leads to negative therapeutic outcomes and financial burdens on the healthcare system. This study aims to compare the mean adherence scores among patients with five dermatological diseases and four treatment types and to identify the associated patient-related factors.Patients and methodsThis is a cross-sectional study conducted from January 2019 to August 2019. The questionnaire was distributed among patients attending the outpatient dermatology clinic at King Khalid University Hospital, Riyadh, Saudi Arabia. It included 2330 patients who were over 16 years old and diagnosed with any of the five dermatological diseases (psoriasis, chronic dermatitis, acne vulgaris, hair growth disorders, and vitiligo). The 12-item Medication Adherence Scale was used to quantify the mean adherence score.ResultsPatients with psoriasis or chronic dermatitis were less adherent to treatments than patients with acne vulgaris, hair growth disorder, or vitiligo. Oral treatment and phototherapy had higher mean adherence scores than injection or topical treatment. High adherence was found in female, single patients; those who did not feel stigmatized from using treatment; those who did not have bad experience with the treatment; those who did not suffer from forgetfulness; those who connected receiving treatment with a habit; those who did not lack treatment responsiveness; those who had an excellent relationship with a dermatologist; and patients with a lesion in an exposed area. Stepwise multiple linear regression was also used to identify the independent variables related to adherence score.ConclusionPsoriasis and chronic dermatitis patients had the lowest mean adherence scores. Patient who were on oral medication had the highest adherence score, while those on topical medication had the lowest score. The thoughtful consideration of factors associated with high adherence is important for optimal therapeutic outcomes.