Background: In chronic illnesses requiring long-term therapy, such as Rheumatoid Arthritis (RA) and Juvenile Idiopathic Arthritis (JIA), medication non-adherence is a major issue that drives up expenses globally. Adherence is crucial to achieving desired results but is frequently poor during treatments. Objective:Our study aimed to evaluate compliance to DMARDS between Rheumatoid Arthritis patients and Juvenile Idiopathic Arthritis patients by Compliance Questionnaire of Rheumatology (CQR) and factors potentially affecting it. Subjects and methods:Thiscomparative study included two groups: Group (1): 120 rheumatoid arthritis and group (2): 60 juvenile idiopathic arthritis patients. All patients were subjected to: Complete history taking, clinical examination, disease activity assessment, quality of life, anxiety and depression, socioeconomic status and adherence to treatment by Standardized questionnaires.Results: Our study revealed that medication non-adherence was higher in RA group than JIA group with highly significant difference between both groups. Fear of drug side effect was the first cause of disease-modifying antirheumatic drugs (DMARDs) non-adherence in both groups. Also our study found that there was significant difference as regards steroid administration in JIA group and DMARD non adherence. There was significant value regarding depression and DMARD non-adherence in RA group. As regards socioeconomic status and DMARD non-adherence, there was significant difference among RA group. Conclusion: RA group had a greater rate of DMARDS non-adherence than JIA group. Non-adherence is a complex issue that is impacted by a number of variables. These variables may be separated into five categories: Social and economic variables, treatment-related factors, disease-related factors, patient-related factors, and factors associated to the health care system.