AIMS: To investigate the relationship between potential explanatory factors (socio-economic factors and health) and non-response in two general population health interview surveys (face-to-face and telephone), and to compare the effects of the two interview modes on non-response patterns. METHODS: Data derives from The Danish Health Interview Survey 2000 (face-to-face interview) and The Funen County Health Survey 2000/2001 (telephone interview). Data on all invited individuals were obtained from administrative registers and linked to survey data at individual level. Multiple logistic regression analyses were used to examine associations between potential explanatory factors and non-response. RESULTS: The overall response rate was higher in the face-to-face interview survey (74.5%) than in the telephone survey (69.2%). Refusal was the most common reason for non-response and the same factors were generally associated with non-response in both modes of interview. The non-response rate was high among persons with low socio-economic position. No significant associations between health and non-response were found. CONCLUSIONS: Health status does not play a systematic role for non-response rates in health interview surveys, but the non-response rate is higher in lower socio-economic groups. Analyses of non-response should be performed to understand the implications of survey findings.