Aim: To examine the non-adherence to drug therapy in chronic haemodialysis (HD) patients, in terms of prescribed and actually taken drugs (”persistence”), and in relation to their age. To determine the adherence using the questionnaire to find out whether the patients are taking the drugs (”execution”) and to examine the relation between ”persistence” and ”execution”. To identify the patients who need additional support due to non-adherence in taking their prescribed drugs. Patients and methods: Study included 127 chronic HD patients (75 males) at Clinical Hospital Centre Osijek (CHCO). Demographics and general medical data were taken from the medical records and data on the prescribed drugs from dialysis protocols. The patients were asked to bring all the drugs that they were taking to determine the “persistence”. The End Stage Renal Disease Adherence Questionnaire on omitting to take drugs was performed. The data on the prescribed drugs, the drugs that were actually taken, and the drugs that were omitted were compared. Results: 19 patients (15 %) did not fill in the questionnaire and 36 (28 %) of them did not provide the drugs that they were actually taking. For 91 (72 %) of the patients who brought their drugs, 7.2 kinds of drugs (SD 3) were prescribed and they were actually taking 6.5 kinds of drugs on average (SD 3.1), P = 0.005. There was no difference in adherence in relation to the patients’ age. Around two thirds of the patients answered that they did not omit to take drugs or that they did it very rarely. Conclusion: Majority of the chronic HD patients at the CHCO adhered to the drug therapy, although statistically the number of the drugs they were actually taking was significantly lower than the number of the drugs they were prescribed. However, the difference was not large. The answers to the questionnaire showed that most of the patients did not omit to take their drugs. The adherence was not related to the patients’ age. The questionnaire was a good indicator of adherence and a good tool for identifying non-adherent patients who require special attention, even though the “execution” which was examined in the questionnaire did not relate to the “persistence” (the difference between the prescribed kinds of drugs and the kinds of drugs that were actually being taken), as the other mode of non-adherence. However, even this smaller proportion of non-adherent patients requires additional efforts by physicians and nurses in communication and support regarding regular taking of all prescribed medication.