This paper analyses the interaction between data needs and objective formulation in Strategic Environmental Assessment (SEA). This topic is discussed from the experiences that were gained by designing and applying a participative SEA pre-study process in the developing region of the Sonso Lagoon, Colombia. Data collection and issue identification are described, as are the different purposes and similarities with objective-led and baseline-led SEAs. It is argued that the participative framework used in Sonso can be applied in similar developing country contexts where there is a lack of environmental data and clear development goals. Finally, it is stressed that the participative SEA pre-study process can be implemented in situations where different sector objectives conflict or in circumstances where there is a need to formulate regional or municipal development objectives.