Modernization of passenger cars and constant development of existing legislation lead to a reduction of exhaust emissions from these vehicles. In accordance with package 3 of the RDE test procedure, the European Commission has extended testing methods by including exhaust emissions during a cold start. The article compares the research results on the impact of ambient temperature during the cold start of spark-ignition and compression-ignition engines in road emission tests. The tests were carried out in line with the requirements of the RDE test procedure for passenger cars meeting the Euro 6d-Temp emissions standard. The obtained results were analyzed, i.e. there were compared the engine and vehicle operation parameters and the values of road exhaust emissions, during the cold start of gasoline and diesel engines at the ambient temperature of approximately 25oC.The summary presents the share of cold start phase of a passenger car (at the ambient temperature of around 25oC) for each exhaust emission compound in the urban part of the test, and in the entire RDE test, depending on the engine type used.