This article analysis the relationship between urbanisation processes and the functions and role of planning, using the case study of the Lisbon Metropolitan Area (LMA). It is based on two research projects on the LMA, one already finished and another one still in progress developed by research teams in four schools of the UTL. The information comes from two different levels of analysis: i) the study of urbanisation processes through different decades for the identification of tendencies and for an understanding of the development of the urban metropolitan condition, and ii) the study of different planning proposals and regulations for assessing the efficacy of the urban and governance regulatory system. The article is organised in four parts. The first part summarises and defines concepts for analysing urbanisation processes and trends. The second part refers to the results and the conclusions arising from the study of land use dynamics and changes taking place in the LMA through different periods. In the third part these results are evaluated in face of municipal planning proposals and land use regulations. The last part tries to draw conclusions based on convergences and divergences between urbanisation dynamics and conditions for planning control and planning practice, particularly in terms of the role of public investment policies.