This dissertation aims at developing a comparative study between the strategic planning processes of two social complex systems, the cities of Rio de Janeiro and Porto Alegre. The adequacy of the planning methodologies used in these processes is analyzed, in view of the characteristics of each of these systems. The study is based on a review of some approaches to strategic planning, including the line of the Design School and the two currents of the Adaptive Planning, describing, for each of these currents, two methodologies. The two systems are also described, as well as their planning processes. Among the main results, there is the identification of Rio de Janeiro`s planning process with the Strategic Planning approach, whereas Porto Alegre`s can be identified with the non-synoptic line of the Adaptive Planning approach. Some similarities were identified between Porto Alegre`s planning process and the Articulated Incrementalism, such as the use of the Participative Budgeting System, implemented in that city more than ten years ago, which can be identified to the Articulating Instrument, a key element to that approach.