OBJECTIVES: To compare numbers of admissions and days of hospitalization related to the diagnosis in a group of Chronic obstructive pulmonary disease (COPD), before and after their status as beneficiaries of a Pharmacotherapy Monitoring (PM). METHODS: Descriptive study, retrospective and comparison of results for a sample of patients (N = 422) a year before and one year after receiving the intervention by PM; during this period they were recorded and classified as related or unrelated to the diagnosis COPD, all hospital admissions of patients, were quantified per stay days and a vector difference between the days before and after was built. RESULTS: Before the intervention by PM, 24% of patients had at least one hospital admission versus a 19% after; average length of stay before and after for both cases was 13 days with standard deviations of 11 and 13 respectively. 18% of the patients reported a decrease in the length of stay days, 66% remained the same and 15% reported an increase. The differences in the sociodemographic characteristics of patients with decreases and increases in the length of stay were those belonging to the average age (79 and 73 respectively) and schooling, where 22% of patients who had increases in the length of stay achieved at least high school degree compared with 34% of those who decreased. CONCLUSIONS: The comparison using descriptive statistics shows that the outcomes may be the result of intervention by PM. The significance of schooling outcomes lies in that the interventions made by PM, 72% are educating the patient / caregiver, which implies that a higher educational level would reflect greater response capacity. This work is a first step in a cohort comparison study.