Introduction:Adherence as a concept includes various types of health-related behavior. Better medical adherence leads to improved disease control and fewer diabetes–related complications. Quality of life and medication adherence are interrelated. Patients with diabetes who adhere to their treatment can experience an improvement in quality of life and vice versa.Aim:To assess treatment adherence in patients with type II diabetes, as well as the connection between adherence and quality of life.Methodology:A descriptive non-experimental study was conducted in a provincial hospital in Northern Greece. The sample examined was a convenience sample consisting of 108 patients with type II diabetes mellitus. They completed the “Diabetes Self-Care Activities Questionnaire” and SF-36 “Quality of Life Questionnaire”.Results:Participants demonstrated good adherence to diet and blood test / blood glucose test routines, but did not experience high levels of quality of life. The type of treatment affected the adherence to blood tests with a statistically significant difference (p=0,000). Also, marital status affected mental health with a statistically significant difference (p=0,032). The adherence sub scales are correlated with the all domains of quality of life.Conclusions:According to our findings, it is important to plan interventions to enhance adherence to other types of treatment and to help patients to further improve their quality of life.