The shrinking city phenomenon is a multidimensional process, comprising cities, parts of cities or metropolitan areas that have experienced dramatic decline in their economic and social base. Shrinking cities can be defined as 'urban areas that have experienced population loss, economic downturn, employment decline and social problems as symptoms of a structural crisis' (Martinez-Fernandez et al., 2012, 213). Urban decline and the loss of employment opportunities are closely linked in a downwards spiral, leading to an out-migration of population (Pallagst, 2008).The existing body of literature on shrinking cities has shown that the loss of urban population is not entirely a new phenomenon (ARL, 1995; Gob, 1977; Hausermann and Siebel, 1987; Oswalt, 2004). What is new, however, is the extent to which shrinkage occurs on a global scale, and the complexity of its causes (Pallagst et al., 2013). Meanwhile, shrinking cities have become a worldwide, multidimensional phenomenon appearing in many post-industrialised societies., For many years this phenomenon has been widely under-represented in international comparative urban and regional research, thus from the year 2005 on, 'shrinking cities' were labelled an emerging topic in spatial planning. This special issue extends the debate by adding a typology of phases of shrinkage, which are based on the authors' observations of policy responses in shrinking cities. These phases are labelled expansive strategy; maintenance strategy; and planning for decline, as outlined in more detail in the paper by Pallagst et al in this thematic issue. The articles reflect on these different phases by showcasing responses at municipal level to the challenges of shrinkage.While the industrialisation era of the nineteenth century was characterised by urban growth, many of these cities started to shrink in the following century. According to Oswalt and Rieniets (2006, 6), since 1950 more than 350 large cities worldwide have lost a significant proportion of their population. Furthermore, shrinkage often reinforces itself, labelled as a 'downward spiral' or 'vicious circle', where characteristic features are out-migration, rising unemployment, a decrease of purchasing power and shortfall in public revenues. The decline of population and jobs is accentuated by reductions in economic investment and public infrastructure (Fritsche et al., 2007). The complexity of factors enhances the need to embed policies that address shrinkage into local planning instruments and regulations (Cunningham-Sabot et al., 2013; Martinez-Fernandez et al., 2016).Moreover, the notion of shrinkage is sometimes considered as 'conceptually incoherent' as there is still no consensus among scholars, planners, politicians or the public about what shrinkage actually is and how shrinkage should be addressed (Hollander et al., 2009; Olsen, 2013; Bernt, 2015). Hollander et al. (2009, 232) argue that 'if there were more, better, and especially cross-national research on shrinkage, the on-the-ground truth might turn out to be more complex and interesting', expanding beyond the common growth paradigm in planning.Applying the 'right' strategies when it comes to the future development of a shrinking city seems to be crucial. However, there is little clarity on these strategies' effectiveness. Hollander et al. (2009, 232) claim that 'shaving the edges off Youngstown, or Detroit or Dresden, will no longer suffice'. According to Martinez et al. (2016), policy responses need to consider both the global forces behind shrinkage and the particular characteristics of the local context.This thematic issue addresses a wide range of approaches to these questions, and produces evidence from both quantitative and qualitative empirical research. Are shrinking cities still perceived as a taboo in some countries? Can shrinking cities, in a context of limited financial resources, be considered as opportunities with multiple modes of expression such as an improved environmental quality, or as testing grounds for new innovative economic prospects, or new modes of governance? …