Functioning is recognized increasingly as an important study outcome with head and neck cancer (HNC). The International Classification of Functioning, Disability and Health, as adopted by the World Health Organization in 2001, is based on a comprehensive bio-psycho-social view. The objective of this study was to evaluate functioning from the patient perspective and to classify the results using the comprehensive view of the ICF. Patients with HNC were interviewed on their problems in daily life using qualitative methodology. Sampling of patients followed the maximum variation strategy. Sample size was determined by saturation. All individual interviews were digitally recorded and transcribed verbatim. Interview texts were divided into meaning units and the concepts contained in the meaning units were linked to the ICF according to established linking rules. The transcribed data were analyzed and linked by a second health professional and the degree of consensus was calculated using kappa statistics. Concordance of identified ICF categories among different tumor locations was also measured with kappa statistics. Until saturation was reached, 18 patients were interviewed: seven patients with oral cancer, five with hypopharyngeal cancer and six with laryngeal cancer. Thousand four hundred and sixty-two (1,462) different concepts were translated into the ICF using 104 different, second-level ICF categories. These ICF categories are presented in detail. From the patient perspective, the ICF components (a) Body functions, (b) Activities and participation and (c) contextual Environmental factors are equally represented, while (d) Body structures show by far the least number of categories. The concordance between different tumor locations rages between 0.53 and 0.58 (confidence interval 0.42–0.70). The degree of consensus in the linking process was 0.58 (confidence interval 0.45–0.73). The ICF classification can display problems with functioning following HNC sufficiently. For patients with HNC Body functions, Activities and participation in every-day life and contextual Environmental factors are equally relevant. Therefore, rehabilitation of these patients must not confine itself to anatomical and (patho-) physiologic changes, but should move towards a more comprehensive view including the individual patient’s demands on daily life and the given individual contextual circumstances.