Data visualization aids have become popular tools to assist managerial decision making in marketing. For example, Geographical Information Systems (GIS) are often used to identify suitable retail locations, regional distributions for advertising campaigns, or targeting of direct marketing activities. GIS-based visualizations facilitate the assessment of store locations and help planners to select the most promising options. The selection of the best alternative requires a “visual optimization” which is typically supported by GIS–thematic maps. In an online experiment, we investigate the way how different GIS-based data representations influence marketing analysts’ decision making styles. Our results show that GIS-maps are a relevant part of the task environment and that the type of map visualization influences the activated decision processes. The invoked decision process is also shown to depend on the way symbol overload is handled by GIS-maps. We further find that analysts’ decision processes vary under time pressure and also relate to personal characteristics.