Hybrid electric vehicles (HEVs) have an increasing presence in passenger transport segment. They have been designed to minimize energy consumption and pollutant emission. However, the actual performance of HEVs depends on the dynamic conditions in which they are used, and vehicle speed is one of the key factors. A lot of excess emission and fuel consumption can be attributed to rapid changes of vehicle speed, i.e. accelerations and decelerations. On the other hand, dynamic driving favours energy recovery during braking. This study examines the relationship between HEVs speed, pollutant emission and fuel consumption. The considerations were based on the results of testing vehicles in WLTC and NEDC driving cycles, performed on a chassis dynamometer. The test objects were two light-duty passenger vehicles, one with series-parallel, gasoline-electric hybrid system and the other, used as a reference, with conventional spark-ignition engine. Both vehicles had similar technical parameters and combustion engines supplied with gasoline. The driving cycles were divided into several parts according to the speed range. For each part, pollutant emission and fuel consumption were determined and appropriate values of selected parameters of driving pattern were calculated. Combining the results of empirical research and calculated parameters allowed to obtain characteristics. Their analysis provided valuable insight into the impact of driving pattern on actual emission and fuel consumption of HEV.