We discuss the potential and limitations of the metapopulation concept in marine ecology. The usefulness ofthe concept in terrestrial ecology is neither based on its simplicity or generality nor on overwhelming empiricalevidence. The usefulness is in the questions which are asked when the metapopulation concept is applied. Thesequestions address spatial phenomena and processes on different spatial scales. They help in acknowledging that everypopulation, be it terrestrial or marine, has a spatial organization. Understanding this spatial organization is alsoimportant for tackling specific applied problems, i.e. to avoid overexploitation of living marine resources or forconfiguring marine reserves. The 'openness' of coastal populations, whose larvae enter larval pools or which areholoplanktonic, is no reason for not asking the questions implied by the metapopulation concept. For marine ecology,the real problem is to delineate populations, which then may possibly correspond to the 'local populations' ofmetapopulations. Thus, the answer to the question in the title of this paper, whether 'marine metapopulation' is a usefulconcept, is 'yes', if the concept is considered a working hypotheses, if the concept is explicitly defined, and if thequestions linked to the concept are clearly stated. Even if it eventually transpires that only very few marinemetapopulations actually exist, marine ecology would still have gained some important new insights.