Urban air quality is directly associated to vehicle emissions. Although technology of fuel, engines and abate- ment have improved, the incessant increase of the size of the urban fleet promotes further increase in the pollutants by two reasons: more sources and degenerated circulating conditions. In this work, the impacts of different scenarios of Passenger Cars (PC) fleet on hot exhaust emissions were estimated. A bottom-up vehicle emissions inventory was made for five routes in Curitiba, for CO, CO2 , CH4 and NOx. The calculations were performed through an open source software called VEIN (Vehicular Emissions Inventories). The inventory aggregates information from the composition of vehicular fleet (by the distribution of age, fuel and engine size), traffic activity (speed, hourly flow) and emission factors. Five sce- narios of PC fleet were considered, namely, current (age distribution limited to 40 years), and 20 and 30 years limited age distribution, increase and decrease of total PC. The results indicates that the main contributors are older vehicles (30-40 years), for most of inventoried pollutants. Increasing or reducing the PC fleet, for a fixed distribution of age of 40 years, contributes proportionally for the emissions. The results indicate that the model can be an important tool for evaluating vehicle emissions under different urban mobility scenarios.