PurposeThe concept of a smart city, which is relatively new, is analysed from different aspects, including sustainability. Due to rapid urban development, smart city and sustainable city synergy has become an approach supported by the authorities. Hence, the paper aims at assessing and ranking the European Union (EU) capitals in the context of the smart sustainable city (SSC).Design/methodology/approachThe paper assesses and ranks 19 EU capitals according to 41 indicators. The assessment was done in four steps. First, each target SSC indicator was accessed for each city. Second, the scattering results of each city in the list of indicators were noted. Third, the indicators were ranked using the VIsekriterijumska optimisacija i KOmpromisno Resenje (VIKOR) method. And fourth, both scattering and ranking results were compared.FindingsThe comparison of the scattering and ranking results revealed that almost the same cities share the top ten positions. Although two cities fell out of the top ten, the overall results reinforce the reliability of the research results. Amsterdam ranked as the Number 1 SSC, and Helsinki took the second position.Originality/valueA comparison of a wide range of indicators highlights the current situation and the disparities between EU capitals. The results could help local and national authorities and policymakers increase the sustainability and smartness of cities.