BACKGROUND: Multimorbidity and polypharmacy pose challenges to improving the quality of care. OBJECTIVES: To determine the association between prescription of recommended treatment in ambulatory patients with chronic heart failure and multiple comorbidities and hospitalisation events. DESIGN: A population-based retrospective cohort study in Catalonia (north-east Spain). PARTICIPANTS: We included 7173 newly registered patients with chronic heart failure (59% women; mean [SD] age 76.3 [10.7] years). Patients were selected from the electronic patient records of primary care practices and followed for three years. OUTCOME MEASURES: Prescription of angiotensin-converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs) and beta-blockers (BBs). RESULTS: Prescription of ACEI/ARBs in patients managed in primary care without a hospitalisation event during the follow-up rose from 50.8 to 83.5% for 0 and >/=4 comorbidities, respectively, and for ACEI/ARBs and BB from 13.1 to 30.6% for 0 and >/=4 comorbidities respectively. Patients with a hospitalisation event were treated more often (ACEI/ARBs or 1.47 [1.17 to 1.85]; ACEI/ARBs and BB or 1.41 [1.17 to 1.69]). Comorbid conditions receiving more treatment were hypertension (ACEI/ARBs or 3.75 [3.33 to 4.22]; ACEI/ARBs and BB or 1.40 [1.23 to 1.59]), diabetes mellitus (ACEI/ARBs or 1.79 [1.57 to 2.04]; ACEI/ARBs and BB or 1.33 [1.18 to 1.49]) and ischaemic heart disease (ACEI/ARBs or 1.25 [1.10 to 1.42]; ACEI/ARBs and BB or 3.01 [2.68 to 3.38]). CONCLUSION: Prescription of recommended treatment in patients with chronic heart failure increased as the number of comorbidities increased. Family physicians can provide equivalent care to more complex patients and those less complex, according to the number of comorbidities.