OBJECTIVES: As comorbidity has a direct impact on choice of cancer treatment and patient prognosis after diagnosis, this study compared the prevalence and incidence of comorbidity among head and neck cancer (HNC) patients to a cancer-free population in the Netherlands. METHODS: Patients diagnosed with oral cavity, pharynx (excluding nasopharynx), and larynx cancer between 2000-2006 were selected from the PHARMO RLS and Eindhoven Cancer Registry. Each HNC patient was matched by age and gender to four cancer-free controls selected from the PHARMO RLS with date of cancer diagnosis selected as the index date for both cohorts. Comorbidities including diabetes, cardiovascular disease (CVD), anaemia, asthma/COPD, pneumonia, and depression were identified by prescription and/or hospitalisation data. Prevalence ratios and hazard ratios (HRs) were used to compare the occurence of events before and after diagnosis, respectively. RESULTS: Patients diagnosed with oral cavity, pharynx (excluding nasopharynx), and larynx cancer between 2000-2006 were selected from the PHARMO RLS and Eindhoven Cancer Registry. Each HNC patient was matched by age and gender to four cancer-free controls selected from the PHARMO RLS with date of cancer diagnosis selected as the index date for both cohorts. Comorbidities including diabetes, cardiovascular disease (CVD), anaemia, asthma/COPD, pneumonia, and depression were identified by prescription and/or hospitalisation data. Prevalence ratios and hazard ratios (HRs) were used to compare the occurence of events before and after diagnosis, respectively. CONCLUSIONS: HNC patients suffer from significantly higher prevalence and incidence of both chronic and acute comorbidies, compared to cancer-free controls. These conditions may affect patient eligibity for aggressive treatment and place them at higher mortality risk.