Patient non-compliance is a phenomenon which physician meets in his every-day practice. It covers different aspects of patient behaviour, but the most important role plays non-compliance with medication. Medication non-compliance is common among patients, with no respect to kind of disease or its severity. The consequences of non-compliance are serious. The inefficacy of conducted treatment, patient health status deterioration, additional hospitalisations or even deaths are some of them. Another negative influence of patient non-compliance is the increase of health system expenses. Nevertheless, numerous physicians are not fully conscious of this problem and its consequences, although in many instances treatment failure is caused by lack of patient adherence to medication. Many useful methods of compliance improvement are attainable in every physician work. Their broader use may lead to better therapy effectiveness.