The urban densification projects launched in many Swedish cities in recent years supposedly lead to more sustainable urban environments, according to those responsible; solving the shortage of housing units and using the urban infrastructure and other resources in a more efficient way. But many of the proposed projects face a lot of criticism when they are located within the Million Homes Programme areas due to their current situation: social segregation, unemployment, as well as the perception of the permanent increase in insecurity. The voices that are raised against these projects go mainly against their models of conception and management; because those projects will not solve the social problems of the current residents; on the contrary, they will further exacerbate social differences within the city. The main hypothesis of this work is that since much regeneration or urban densification projects have already been carried out within the Million Homes Programme areas, then there must also be some good examples that should be identified and used as a reference to improve the urban regeneration practices in those types of areas. The aim of this study is to investigate if within these new projects there are some that could be considered as better practices of how to do more sustainable urban densification processes in those Million Homes Programme areas. For that the concepts of legitimacy and sustainability are crucial variables to evaluate and identify them. Due to the limitations of the work, the first part identifies and performs a general comparative analysis of six densification projects developed within neighbourhoods built under the Million Homes Programme located in the cities of Malmö and Växjö. In the second part, after a critical analysis two projects are chosen that could be considered as the better practices and perform a second critical analysis to both in a deeper way, to generate the necessary discussion and finally reach conclusions and recommendations. The work is based on qualitative research and complemented with grounded theory and case-study theory, (flexible design), those that served to design specific tools for the analysis purposes of the cases. Among the main findings during the research process were that the failures or weaknesses of some projects are mainly due to the lack of social commitment with local residents (many of them immersed in vulnerable economic and social situations) due to the distancing of the public agencies (municipalities) of the project, while in other projects a social agenda has been incorporated as part of the processes in favour of current residents, which also means the permanent commitment of local governments to these projects, actions that contribute to greater possibilities of achieving sustainability.