Attention deficit hyperactivity disorder (ADHD) is one of the most common psychological pathologies worldwide. Despite mostly occurring in childhood, it could lead to difficulties in adults, mainly on social relations, personal life and performance in work or study.At present, novel technological approaches, such as interactive tools in mixed and virtual reality (VR), have proven to enhance the traditional therapies to reduce the observation dependency and subjectivity. However, usage is still not widespread due to higher costs, field implementation difficulties (e.g., electroencephalography or electrooculography), or being only pediatric-oriented. Therefore, the following research aimed to design and evaluate an immersive Virtual Reality game based on the psychological evaluation of the Continuous Performance Test (CPT) to quantify and supervise the ADHD symptoms, and test any improvement.The game design methodology, measuring techniques and data analysis are presented. A controlled experiment was carried out with 37 participants randomly assigned to two immersion groups: a VR version developed in Unity vs Real version of a custom-made table tennis game, designed to assess nine ADHD-related symptom indicators. All participants performed the activity three times (once per week) to test the individual effect of time and its interaction with the level of immersion. Results suggested greater impulsivity and cognitive flexibility when performing the therapy in VR than in real table tennis, whereas no significant differences were found between the three weekly sessions.