Education and health literacy potentially limit a person's ability to be involved in decisions about their health. Few studies, however, have explored understandings and experiences of involvement in decision making among patients varying in education and health literacy. This paper reports on a qualitative interview study of 73 men and women living in Sydney, Australia, with varying education and functional health literacy levels. Participants were recruited from a community sample with lower educational attainment, plus an educated sample of University of Sydney alumni. The transcripts were analysed using the 'Framework' approach, a matrix-based method of thematic analysis. We found that participants with different education conceptualised their involvement in decision making in diverse ways. Participants with higher education appeared to conceive their involvement as sharing the responsibility with the doctor throughout the decision-making process. This entailed verifying the credibility of the information and exploring options beyond those presented in the consultation. They also viewed themselves as helping others in their health decisions and acting as information resources. In contrast, participants with lower education appeared to conceive their involvement in terms of consenting to an option recommended by the doctor, and having responsibility for the ultimate decision, to agree or disagree with the recommendation. They also described how relatives and friends sought information on their behalf and played a key role in their decisions. Both education groups described how aspects of the patient-practitioner relationship (e.g. continuity, negotiation, trust) and the practitioner's interpersonal communication skills influenced their involvement. Health information served a variety of needs for all groups (e.g. supporting psychosocial, practical and decision support needs). These findings have practical implications for how to involve patients with different education and literacy levels in decision making, and highlight the important role of the patient-practitioner relationship in the process of decision making.