The aim of this study was to systematically identify the type and severity of all comorbid conditions in a cohort of 180 patients with laryngeal squamous cancer. The authors retrospectively surveyed the notes using the Adult Comorbidity Evaluation −27 index (ACE−27) and applying a systematic process of data abstraction that had previously been shown to be accurate and reliable. The results provided insight into the distribution, site and extent of decompensation caused by comorbidity. It was found that 116 (64.4 per cent) of 180 patients in the study population had some form of comorbid illness, with the cardiovascular and respiratory systems being the top two body systems affected in 43.9 per cent and 24.1 per cent respectively. One-quarter (25.8 per cent) of these 116 patients had comorbid illnesses in more than one body system. Concurrent neurological disease is associated with high mortality. The ACE − 27 is a comprehensive instrument that codes all forms of comorbid diseases in the head and neck cancer setting excepting malnutrition. This study suggests that routine collection of comorbidity will be important in future outcomes analysis and in comparing treatment results between centres. Apparent improvements in treatment outcome following newer therapeutic modalities will have to take into account any changes in the comorbidity type and burden over time.