Cohen, March, and Olsen (1972), the proponents of the garbage-can model, develop a simulation model for examining decision-making in organized anarchies. From the simulation model, they conclude that unsegmented organization structure makes resolution of problems uncommon and increases decisions by oversight and flight. However, it would be natural that unsegmented structure enables many decision-makers to work together and enhances problem-solving performance. This study examines how unsegmented structure enhances or hinders problem-solving and what decision processes the structure causes, using a simulation based on Cohen et al. ‘s (1972) model. The simulation results of this study are as follows. (1) Unsegmented structure does not change the amount of resolution dramatically; rather, it improves problem-solving performance when the organization is not required to make decisions frequently. (2) The less unsegmented the organization structure becomes, the more problems become invisible and overlooked; that is, decisions by oversight increase radically. (3) The more unsegmented the organization structure becomes, the more problems become visible but come to remain unsolved; that is, decisions by flight increase radically. Finally, this study also discusses nonterritorial office cases as an application of the simulation results.