Chronic obstructive pulmonary disease (COPD) is one of the most severe public health problems and a leading cause of death worldwide. One of the main reasons for poor control of the disease is low patient compliance with treatment plan. The aim of the study was to investigate sociodemographic and health status factors that may have an influence on adherence to treatment. There were 106 inpatients (F/M, 42/64; mean age 70 ± 6 years) with COPD enrolled into this retrospective study. Patients completed the Adherence to Refills and Medications Scale (ARMS) to assess adherence to therapy. We found that the mean ARMS score was 23.1 ± 6.8. About 86% of patients had low adherence, and 14% had good adherence (mean score 3.2 ± 2.4). The low-adherence patients were more likely to be older (p = 0.020), female (p = 0.011), single (p = 0.019), not professionally active (p = 0.049), hospitalized more often (p = 0.005) and for a longer time (p = 0.046), feel worse (p = 0.023), experience a greater impact of the disease on sleep quality (p = 0.008) and daily activities (p = 0.001), and had a higher GOLD stage of COPD when compared to patients with good adherence patients (p = 0.012). Multiple factor analysis demonstrates that independent adverse predictors of the ARMS score included the following: being single (OR = 3.18), having had more than eight hospitalizations (OR = 1.18), and experiencing dysfunction in daily activities (OR = 1.79). Male gender (OR = 0.77) and longer than 21-day hospitalizations (OR = 0.93) were independent positive predictors of adherence. In conclusion, COPD patients demonstrate a low level of adherence to pharmacotherapy. Adherence is adversely affected by sociodemographic (older age, female gender, being single, and professionally inactive) and clinical factors (more frequent hospitalizations, perception of poor well-being, disordered sleep and daily functioning, and a higher GOLD stage).