Out-of-pocket patient payments are a major source of health care funding in Central and Eastern European (CEE) countries. They take different forms, e.g. formal co-payments, quasiformal charges and informal patient payments. Formal co-payments are regulated by national legislation and quasi-formal charges are set by the health care provider in the absence of clear government regulations. Informal payments (also known as “under-the-table” or “envelope” payments) comprise all unregistered patient payments for publicly-funded health care services. Informal patient payments claim more attention as ignoring these payments causes underestimation of total health expenditure and their hidden nature imposes a great challenge to health care provision in terms of accessibility as well as accountability and transparency. Overall, a huge variety in the nature and patterns of informal patient payments is reported across countries. Studies provide evidence on the variation in informal payment type (cash or in-kind gifts given by patients or their families), timing (before, after or during service provision), subject (out- or in-patient service), purpose (obtaining better quality or access), and motivation (physician’s request or patient’s initiative). As recent cross-country studies on informal patient payments are lacking, this dissertation enhances our understanding of informal patient payments by comparing their scale and pattern across CEE.