Problematic Internet use (PIU), which has become a global social issue, can be broadly conceptualized as an inability to control one's use of the Internet which leads to negative consequences in daily life. The aim of this paper is to give a brief overview of the gradually evolving body of literature on PIU. This shows that the definitions and diagnostic criteria that have been proposed, and the assessment tools that have been developed, stress similarities between PIU, addictive behaviours and impulse-control disorders. Disagreements regarding diagnostic criteria and the lack of large epidemiological studies have resulted in difficulties in establishing the prevalence of PIU in the general population. Studies suggest high comorbidity rates between PIU and numerous psychiatric disorders highlighting the importance of focusing on comorbidity in treatment. There is growing evidence that genetic, personality and individual differences in automatic and controlled aspects of self-regulation may promote the development of PIU. Pharmacological and psychotherapeutic treatments specific to PIU have received limited testing in large, rigorous studies however preliminary evidence suggests that both psychotropic medications (Escitalopram, Naltrexone and Methylphenidate) and cognitive behaviour therapy may have some utility in the treatment of PIU. More research is needed on areas which remain unclear and contribute to the prognosis of PIU, in particular the temporal relationships between psychiatric disorder and PIU, mechanisms of comorbidity and the more subtle psychological changes that occur through Internet use.