Problematic Internet use appears to be a growing concern in many criminal and civil legal proceedings. Problems range from inappropriate personal use of the Internet in the workplace and excessive use of online games, pornography, and gambling, to cyberbullying among children and adolescents and numerous forms of criminal activity. Forensic psychiatric evaluations may help courts or other agencies to understand individual cases and to discern whether a psychiatric disability may be involved. Furthermore, the forensic psychiatrist may be asked to formulate a prognosis or to suggest which treatments may be helpful. Among the multiple underlying pathophysiologic mechanisms that explain problematic Internet use are: addiction, compulsion, impulse-control problems, and mood disorders. There is no definitive or standard treatment protocol for evaluation or treatment of problematic Internet use per se. A comprehensive evaluation should address the underlying psychopathology or personal problems that prompt or contribute to the problematic Internet use. This article suggests approaches that may help forensic psychiatrists to conduct a thorough evaluation with reasonable treatment recommendations. Different formulations of the problem and a discussion of DSM-IV factors are offered to provide starting points for the evaluation and to help psychiatrists to understand how problematic Internet use may relate to Axis I disorders or other factors.