Various institutional and cultural settings have shaped spatial planning systems with comparable features; however, such systems have been adapted to specific cultural, normative and spatial conditions. In line with the growing demand for international knowledge exchange in urban and regional planning, planning cultures have recently come into sharper focus. Moreover, it has become widely acknowledged that many cities in Europe and the USA have to deal with challenges posed by long-term demographic and economic changes. This also holds true for Japan. The objective of the research presented here is to comparatively investigate changes in planning cultures in view of shrinking cities in the USA, Germany and Japan. The findings will allow us to detect interdependencies between changes in planning cultures and societal changes in the wake of shrinkage, and finally to derive hypotheses for both the future-oriented development of shrinking cities, and the development of planning cultures based on the comparison of cultural settings. In this respect the paper concludes with the hypothesis that there might be planning cultures that are not framed by geographic entities (nations, regions, cities), but rather by topics along shrinking cities. This could offer insight into a new research sphere of 'topical planning cultures'. While lasting effects and successes of policies and strategies applied in shrinking cities remain to be seen, their influence on a broader knowledge exchange, contextualisation and innovation in the sphere of planning cultures is evident.