Chronic diseases constitute a significant threat to health. Worldwide, medication adherence in chronic diseases remains unsatisfactory. Understanding factors affecting adherence is essential. This study examined medication adherence by characteristics of patients with chronic diseases. This cross-sectional study included 800 patients. The Adherence to Chronic Diseases Scale was used to measure adherence. Descriptive statistics and logistic regression was used to examine factors influencing medication adherence. Low adherence was found in 19.5% of the patients, 45% had medium adherence, and 35.5% had high adherence. Logistic regression showed that retired ( 0.496, 95% CI [0.33-0.75]), having COPD ( 0.460, 95% CI [0.32-0.67]) and duration of disease ≤5 years ( 1.554, 95% CI [1.11-2.17]) remain independent predictors for high adherence. Mixed findings regarding the relationship between medication adherence and patients' characteristics were noticed. Patients' characteristics should be examined with the individual population when examining and attempting to improve medication adherence in clinical practice.