Objectives — To assess haemodialysis patients' beliefs about treatment and to investigate which beliefs correlate with adherence to medication and fluid‐diet restrictions. Methods — Forty‐seven haemodialysis patients receiving intermittent hospital haemodialysis completed questionnaires assessing their beliefs about medication and fluid‐diet restrictions. Key findings — Adherence rates varied between and within patients, and were related to specific treatment beliefs in a logically consistent way. Reported intentional non‐adherence to medication correlated with concerns about the potential adverse effects of renal medication. Low adherence to fluid‐diet restrictions (assessed by inter‐dialysis weight gain) was associated with the personal belief that the restrictions were too strict. Most patients (90 per cent) agreed that medicines prescribed for their renal condition were necessary for maintaining health. However, 32 per cent harboured concerns about their medication, arising from beliefs about the potential for dependence, long‐term effects, or disruption of life. Concerns about renal medication correlated with more general beliefs that medicines as a whole are harmful, addictive poisons which are overused by doctors. Although specific treatment beliefs (medication or fluid‐diet restrictions) were related to specific adherence behaviours, these two areas of beliefs and behaviours were unrelated. Conclusions — Patients' perceptions of treatment merit further study. Eliciting and addressing patients' perceptions of treatment may be a target for pharmaceutical care and a foundation for partnership in medicine‐taking.