Overall attendance in the Forum rose from 1,200 at the inaugural session in Nairobi in 2002, to over 4,300 in Barcelona in 2004 and over 10,400 in Vancouver in 2006. In Nanjing in 2008, there were 8,000 participants, their numbers reached almost 13,800 at the fifth session in Rio de Janeiro in 2010 and over 8,200 attended the sixth session in Naples in September 2012. One hundred countries were represented at the third session, 146 at the fourth, 150 at the fifth session and the sixth session in Naples saw a record number of 152 countries represented. 

The third session of the Forum, held in Vancouver in 2006 (the thirtieth birthday of UN-Habitat), focused on sustainable urbanization and inclusive cities. One of the messages from the Forum was that the urban population of developing countries is set to double from 2 to 4 billion in the next 30 years. This will require the equivalent of planning, financing and servicing facilities for a new city of 1 million people to be built every week for the next 30 years. 

The theme of the fourth session of the Forum, held in Nanjing in 2008, was harmonious urbanization. At this session, it was made clear that a society cannot be harmonious if large sections of its population are deprived of basic needs while other sections live in opulence. An important message from this session of the Forum was that harmony in cities cannot be achieved if the price of urban living is paid by the environment. The concept of harmony entails the synchronization and integration of all the Earth’s assets: physical, environmental, cultural, historical, social or human. 

The fifth session of the Forum was held in Rio de Janeiro, and it built upon the technical and substantive lessons of the previous four sessions. It focused on the theme of “Right to the city: bridging the urban divide”. The Forum shared perspectives and viewpoints on the relevance of this concept, identifying what is needed to bridge the urban divide and to facilitate a prompt and sustainable transition from a city that is partially inclusive to one that is fully inclusive. The sixth session, held in Naples, had as its main theme ‘The Urban Future’ a broad theme that encouraged reflections on the current and future challenges of our cities. The seventh session was held in Medellín, Colombia, with the focus on "Urban Equity in Development – Cities for Life". The ninth session of the Forum has taken place in 2018 in Kuala Lumpur, Malaysia.