The measurement of health-related quality of life (HRQOL) in children often relies on parents as proxy respondents. Yet, several studies have shown poor to moderate correlations between parent and child responses, questioning the validity of the parent as proxy. This qualitative study examined a dyad approach, where parent and child were interviewed together. The objective was to observe and describe the interaction in a dyad interview, wherein both parent and child perspectives are used and where the parent may expand the child's cognitive abilities to create a more meaningful description of the child's HRQOL. Children aged 8-15 years with a clinical diagnosis of asthma and their primary caregivers were recruited from The Hospital for Sick Children, Toronto, Canada. The dyads were administered the Health Utilities Index Mark II/III, the Pediatric Asthma Quality of Life Questionnaire and the PedsQL Pediatric Quality of Life Inventory. Interviews were audio-taped and a second researcher recorded observations. Consistent with Grounded Theory methodology, observations were indexed according to categories and subcategories related to the response process. Data were analysed using open, axial and selective coding and constant comparison. Saturation was achieved at 16 dyad interviews. A cultural review and reflexive role taking were included to minimize interviewer bias and enhance rigour. Findings were grouped in the following 11 themes: recall difficulty, respondent bias, interviewer bias, frustration, coercion/parental influence, inter-relational conflict, psychic discomfort for health states, emotional sensitivity, parent as advocate, parent as enabler and comprehension. The specification of these categories facilitated the creation of an interview guide to accompany the administration of standardized HRQOL questionnaires to parent-child dyads. Such a guide would facilitate discussion between parent and child and enhance the consistency of the interview process.