In March 2010 an Expert survey among the Action members in the COST Action "Cities Regrowing Smaller" (CIRES) was launched. In order to generate knowledge on regeneration strategies in shrinking cities in Europe, shrinking cities need to be analysed and described. Therefore, the survey focuses on the aspects which must be taken into account to describe shrinkage. The results represent the opinion of a unique group of experts with a broad knowledge base on population decrease and urban decline in 26 European countries.