Abstract. BACKGROUND: Smartphones have become an integral part of our lives, providing a wide range of useful features. However, it is important to address the potential risks of using a smartphone while performing motor tasks. AIM: To investigate the effects of smartphone use on postural control and mobility in young adults during standing or walking activities. METHOD: Forty-five individuals, mean age of 22.1 ± 1.5 years, were enrolled in this study. The impact of using smartphone was assessed during a static (performed on a force platform) and a dynamic (timed up and go) test. The participants were instructed to text a message and talk on the phone while standing or walking. Multiple analyses of variance were applied to verify main effect of task. Effect sizes are reported. Significance was set at 5%. RESULTS: Using a smartphone with a simultaneous motor task had a negative impact on both static and dynamic tests (effect size of 0.820 and 0.788, respectively). Participants were at similar risks when walking while texting messages or talking on the phone. Conversely, when standing, talking on the phone caused greater risks compared to the texting condition. INTERPRETATION: In a sample of young adults, smartphone usage was found to affect the performance of motor tasks. The impact varied depending on whether the participants were walking or standing. Further studies should be conducted to investigate the risks associated with performing motor tasks with a smartphone among different population groups, including older individuals and subjects with physical disabilities.