Background: Belgium is currently implementing a nation-wide reform of mental health care delivery based on service networks. These networks are supposed to strengthen the community-based supply of care, reduce the resort to hospitals, and improve the continuity of care. They are also intended to supply comprehensive care to all adult mental health users. It is unclear, however, if one single model of network can target the needs of the whole adult population with mental health problems. Methods: In 2011, ten networks were commissioned and assessed. Networks included a total of 635 services of different types. Services were asked to select 10 users by systematic sampling and to state whether these users were considered as a priority for care in the network. Sociodemographic, social integration level, diagnoses, and psycho-social functioning variables were also collected. Results: Two thousand four hundred ninety users were included, and 1564 were given priority for network care. Priority was higher for men than for women (69.9 % versus 56.2 %), and for non-nationals than for Belgians (72.6 % versus 61.9 %). Users were designated priority when they had poor psycho-social functioning (HoNOS > 17, OR = 3.15, p < 0.001), personality disorder or schizophrenia (OR = 1.54, p < 0.001), and a medium level of social integration (SIX = [2,3], OR = 1.57, p < 0.001). Less socially integrated patients (SIX < 1, OR = 0.53, p < 0.001) and users of community and social services were less likely to be selected. Conclusion: Although the reform was intended for the whole population of adults with mental health problems, the users selected have a profile of severe mentally-ill users with social deprivation and poor social functioning. Policy may have been over-ambitious trying to address the whole population with one single type of service network. The actual selection process of users makes it less likely that the reform will achieve all its objectives.