This paper addresses the research question of how does the complexity of a decision task affect information acquisition strategies used by decision-makers in a GIS-based multicriteria decision analysis (MCDA)? It reports the results of an experimental study that investigated the effect of task complexity (information load) on information acquisition strategies in the use of a multicriteria spatial decision support system (MC-SDSS). The experiment involved the use of the MC-SDSS for online parking site selection (ranking) in District # 22 of Tehran, Iran at four levels of complexity. The complexity of the site selection task was manipulated in terms of the number of: (1) decision alternatives available to decision-makers and (2) the evaluation criteria (attributes) used to describe the alternatives. At each level of task complexity, the site selection process was carried out in two GIS-MCDA modes: individual and group (collaborative) modes. The findings demonstrate that: (1) an increase in task complexity tend to result in the use of non-compensatory decision strategies; (2) decision-makers using compensatory strategies spend more time acquiring information from decision tables than maps, and (3) the task complexity has no impact on the interaction between the map and table uses.