Since the late 1990s health technology assessment (HTA) has gained influence as a research and evaluation approach supporting health care policy. The focus on this methodology is congruent with the growing importance of evidence-based health care. Although HTA is a multidisciplinary discipline from a theoretical point of view, practice shows that social, ethical and psychological aspects are seldom truly integrated into the assessment of health technology. HTA is still very much biased by the medical and pharmaceutical research traditions. This contribution focuses on the question of how qualitative research findings could be useful as an additional source of information or as 'evidence' in HTA. Medical and health care scientists are seldom acquainted with qualitative research or judge it as a less (or un-)reliable form of research. 'Qualitative dimensions' of health care are not considered 'real' evidence. This contribution argues that qualitative findings could be put higher in the hierarchy of evidence generating research in health care. First it can be realized by improving the knowledge of the nature of qualitative research. Second qualitative findings can become more trustworthy information, if researchers themselves respect methodological prerequisites and clarify their theoretical perspective, research aims and use of research methods. Some methodological characteristics of qualitative research and 'evidence' are discussed for their contribution to HTA and evidence-based health care.