BACKGROUND: Out-of-pocket payments for health services constitute a major financial burden for patients in Central and Eastern European (CEE) countries. Individuals who are unable to pay use different coping strategies (e.g. borrowing money or foregoing service utilization), which can have negative consequences on their health and social welfare. This article explores patients' inability to pay for outpatient and hospital services in six CEE countries: Bulgaria, Hungary, Lithuania, Poland, Romania and Ukraine. METHODS: The analysis is based on quantitative data collected in 2010 in nationally representative surveys. Two indicators of inability to pay were considered: the need to borrow money or sell assets and foregoing service utilization. Statistical analyses were applied to investigate associations between the indicators of inability to pay and individual characteristics. RESULTS: Patient payments are most common in Bulgaria, Ukraine, Romania and Lithuania and often include informal payments. Romanian and, particularly, Ukrainian patients most often face difficulties to pay for health services (with approximately 40% of Ukrainian payers borrowing money or selling assets to cover hospital payments and approximately 60% of respondents who need care foregoing services). Inability to pay mainly affects those with poor health and low incomes. CONCLUSION: Widespread patient payments constitute a major financial barrier to health service use in CEE. There is a need to formalize them where they are informal and to take measures to protect vulnerable population groups, especially those with limited possibilities to deal with payment difficulties.