Distracted driving is a significant factor affecting road safety and it can occur as a result of using mobile phones while driving. The aim of the current research is to present the prevalence of mobile phone use by Polish car drivers, based on the roadside and online survey. The field study showed that 11.6% of 1867 drivers were using mobile phones while being in motion and 26.1% of 203 drivers when stopped in front of traffic lights. While moving, 8.9% were manipulating the device by hand and 2.6% – holding it to ear. During the stop, 14.2% of the observed motorists were manipulating it, 3.0% – holding it to the ear, and 8.9% – talking through a hands-free or headset. To determine how many people generally use mobile phones while driving (not only during momentary observation), a questionnaire was also carried out. The vast majority of 252 surveyed drivers (82.9%) admitted to using mobile phones while driving, and an equally large proportion considered this behavior as dangerous for transport safety (81.3%). Most of the motorists reported using cell phones: rarely (44.4%), both when stopped and being in motion (58.9%), in a built-up area (63.6%), holding it in hand (43.5%) and in order to chat or write messages (81.8%). The majority of drivers using cell phones while driving were male and in the 25–44 or 18–24 age group. None of the respondents caused an accident due to the use of these devices, but 1.6% were guilty of a collision caused by this reason.