Objectives: To investigate the occurrence of 27 chronic medical conditions in a cohort of adults with and without hearing impairment, and to examine the association between these conditions and hearing ability. Design: The National Longitudinal Study on Hearing (NL-SH study) is a large prospective study among adults aged 18 to 70 years, conducted via the internet in the Netherlands. Hearing ability was measured with a digits-in-noise test and comorbidity was assessed through self-report. Study sample: Cross-sectional data of 890 hearing-impaired and 975 normally-hearing adults were analyzed. Both descriptive statistics and multinomial logistic regression analyses were conducted. Results: Of the NL-SH participants with insufficient or poor hearing ability, 78.5% reported to suffer from at least one additional chronic condition. This proportion was larger than in the normally-hearing group (68.6% with one or more chronic conditions and 37.7% with two or more). After adjustment for age and gender, 'dizziness causing falling', 'diabetes' and 'arthritis types other than osteoarthritis and rheumatic arthritis' were significantly associated with poor hearing ability. Conclusions: Our results show that some previously reported associations do not only occur in older age groups, but also in younger cohorts. Comorbidity is relevant in the rehabilitation (multi-disciplinary care) and the clinical encounter. © 2014 British Society of Audiology, International Society of Audiology, and Nordic Audiological Society.