BACKGROUND: Several studies have investigated the impact of mobile phone exposure on cognitive function, but mainly in adults. Children and adolescents are of special interest due to their developing nervous systems. METHODS: Data were derived from the Australian Mobile Radiofrequency Phone Exposed Users’ Study (MoRPhEUS) which comprised a baseline examination of year 7 students during 2005/2006 and a one year follow-up. Sociodemographic and exposure data were collected with a questionnaire. Cognitive functions were assessed with a computerized test battery and the Stroop Color-Word test. RESULTS: Overall, 236 students participated in both examinations. The proportion of mobile phone owners as well as the number of voice calls and Short Message Services (SMS) per week increased from baseline to follow-up. Participants with higher numbers of voice calls and SMS at baseline showed lesser reductions in response times over the one year period in some of the computerized tasks. Furthermore, those with an increase in voice call and SMS exposure over the 1 year period showed changes in some of the tasks. No associations were seen between mobile phone exposure and the Stroop test. CONCLUSIONS: We have observed that some changes in cognitive function occurred with a latency period of one year. further that some changes occurred that were associated with an increase in exposure. However, the increase in exposure mainly applied to those who had lesser numbers of voice calls and SMS at baseline.