Architectural simulation techniques - CAD, video montage, endoscopy, full-scale or smaller models, stereoscopy, holography etc. - are common visualizations in planning. A subjective theory of planners says “experts are able to distinguish between'pure design', in their heads and visualized design details and contexts like color, texture, material, brightness, eye level or perspective.” If this is right, simulation details should be compensated mentally by trained people, but act as distractors to the lay mind.  Environmental psychologists specializing in architectural psychology offer “user needs&apos, assessmentsi and “post occupancy evaluationsi to facilitate communication between users and experts. To compare the efficiency of building descriptions, building walkthroughs, regular plans, simulation, and direct, long-time exposition, evaluation has to be evaluated.  Computer visualizations and virtual realities grow more important, but studies on the effects of simulation techniques upon experts and users are rare. As a contribution to the field of architectural simulation, an expert - user comparison of CAD versus endoscopy/model simulations of a Vienna city project was realized in 1995. The Department for Spatial Simulation at the Vienna University of Technology provided diaslides of the planned city development at Aspern showing a) CAD and b) endoscopy photos of small-scale polystyrol models. In an experimental design, they were presented uncommented as images of “PROJECT Ai versus “PROJECT B” to student groups of architects and non-architects at Vienna and Salzburg (n= 95) and assessed by semantic differentials. Two contradictory hypotheses were tested: 1. The “selective framing hypothesis” (SFH) as the subjective theory of planners, postulating different judgement effects (measured by item means of the semantic differential) through selective attention of the planners versus material- and context-bound perception of the untrained users. 2. The “general framing hypothesis” (GFH) postulates typical framing and distraction effects of all simulation techniques affecting experts as well as non-experts.  The experiment showed that-counter-intuitive to expert opinions- framing and distraction were prominent both for experts and lay people (= GFH). A position effect (assessment interaction of CAD and endoscopy) was present with experts and non-experts, too. With empirical evidence for “the medium is the messagei, a more cautious attitude has to be adopted towards simulation products as powerful framing (i.e. perception- and opinion-shaping) devices.