Abstract Background In recent years, there has been a large increase in the use of communication/connected devices and technologies. This raises a question about radiofrequency electromagnetic fields (RF-EMF) exposure levels and neuropsychological effects of RF-EMF in young people. The aim of this study was to assess the pattern of use of communication/connected devices and technologies and its impact on cognition and mental health of early school age children in Poland. Methods The study population consists of 293 children from Polish Mother and Child Cohort (REPRO_PL). The study was based on questionnaire data covering type and duration of usage of communication/connected devices and technologies by mothers during pregnancy and children at age of 7 years. The environmental exposure to RF-EMF was also taken into account. Based on such data RF-EMF exposure was assessed. Child emotional and behavioral assessment was done by Strengths and Difficulties Questionnaire whereas IQ and psychomotor development of children was performed by psychologist using Intelligence and Development Scales. Results About 75% of young people used smartphones (2% for voice calls and 7% for Internet browsing at least one hour per day). Tablet or laptop use was declared by 59% and 56% of respondents, respectively. More than 10% declared that they use these devices at least one hour a day. The main factors determining the use of new technology devices were parental age and education (p < 0.05) and the age at which youth started school education (p = 0.06). In multivariable regression model higher level of RF-EMF was associated with total difficulties and emotional problems (p < 0.05). Conclusions This study presents the pattern of use of new technology devices by early school age children in Poland and the association between the exposure to RF-EMF and child mental health. Key messages • The use of communication/connected devices and technologies is common among young people in Poland. • The exposure to RF-EMF can increase mental health problems among young people.