Background: In the world's strive towards reaching the Sustainable Development Goal 3 (SDG3) as ensuring healthy lives and promoting well-being for all at all ages, Ukraine is not only lagging to reach recommended immunization coverage threshold and showing substantially lower results than the peer countries in the European region but also puts the risks on a stake with recorded poliovirus and measles cases during the last five years. However, there is limited knowledge of the factors underlying the immunization uptake in Ukraine. This research sheds light on the determinants of childhood vaccination and aims to measure and decompose socioeconomic inequalities in the receipt of the third dose of the diphtheria-tetanus-pertussis-containing vaccine (DTP3) in Ukraine. Methods: The analysis was conducted with the use of data from the most recent publicly available Multiple Indicator Cluster Survey performed in Ukraine in 2012. The focal group of this research is children aged between 12 and 23 months. Immunization data was presented disaggregated by the background characteristics. Simple (ratio and difference) and complex (concentration index) measures of inequality were applied for assessing inequality in DTP3 immunization uptake. The Erreygers correction of concentration index was used to quantify and decompose socioeconomic inequalities accompanied by the concentration curve. Results: The results suggest a pro-poor socioeconomic gradient in childhood immunization with the DTP3 vaccine in Ukraine measured by the concentration index (CI=-0.096). The decomposition analysis revealed that a substantial part of inequality was determined by household wealth. Mother's health beliefs and regional disparities were also contributing to inequality, while parental education was following the opposite direction. Conclusion: Specific attention should be directed towards the Northern region while designing regional immunization policies. Tackling possible vaccine hesitancy, the focus should be made on such sources of healthcare information as TV and the Internet, which are negatively affecting the vaccination uptake. Since household economic status was the main factor contributing to pro-poor inequality in DTP3 immunization, further investigation might be needed to identify the reasons for lower vaccination coverage among the wealthier children, especially upon the availability of the new household surveys.Background: In the world's strive towards reaching the Sustainable Development Goal 3 (SDG3) as ensuring healthy lives and promoting well-being for all at all ages, Ukraine is not only lagging to reach recommended immunization coverage threshold and showing substantially lower results than the peer countries in the European region but also puts the risks on a stake with recorded poliovirus and measles cases during the last five years. However, there is limited knowledge of the factors underlying the immunization uptake in Ukraine. This research sheds light on the determinants of childhood vaccination and aims to measure and decompose socioeconomic inequalities in the receipt of the third dose of the diphtheria-tetanus-pertussis-containing vaccine (DTP3) in Ukraine. Methods: The analysis was conducted with the use of data from the most recent publicly available Multiple Indicator Cluster Survey performed in Ukraine in 2012. The focal group of this research is children aged between 12 and 23 months. Immunization data was presented disaggregated by the background characteristics. Simple (ratio and difference) and complex (concentration index) measures of inequality were applied for assessing inequality in DTP3 immunization uptake. The Erreygers correction of concentration index was used to quantify and decompose socioeconomic inequalities accompanied by the concentration curve. Results: The results suggest a pro-poor socioeconomic gradient in childhood immunization with the DTP3 vaccine in Ukraine measured by the concentration index (CI=-0.096). The decomposition analysis revealed that a substantial part of inequality was determined by household wealth. Mother's health beliefs and regional disparities were also contributing to inequality, while parental education was following the opposite direction. Conclusion: Specific attention should be directed towards the Northern region while designing regional immunization policies. Tackling possible vaccine hesitancy, the focus should be made on such sources of healthcare information as TV and the Internet, which are negatively affecting the vaccination uptake. Since household economic status was the main factor contributing to pro-poor inequality in DTP3 immunization, further investigation might be needed to identify the reasons for lower vaccination coverage among the wealthier children, especially upon the availability of the new household surveys.