Nowadays, virtual reality is becoming one of the most innovative methods of diagnosis and therapy as well as psychological and neuropsychological rehabilitation. A virtual environment is created with the use of goggles generating a three-dimensional image. The device induces a state of immersion which can be explained as the sense of presence in a virtually arranged world. As a result of this phenomenon, virtual space tests have high ecological validity, which is an extremely significant aspect for tests employed in psychological diagnosis. The study presents the description of a Virtual Classroom Task applicable in the process of clinical diagnosis, using continuous performance tasks. The method is an alternative way to assess cognitive functions, especially in the case of children suffering from attention-deficit/hyperactivity disorder. The parameters assessed include, above all, attention processes and the inhibition of reaction. The development of virtual space tests creates an opportunity to extend the scope of the measurement techniques used to assess attention processes. Those tests are sophisticated systems aimed at examining the field of vision by following the head movement, especially while presenting a material accompanied by distractors. The stimuli making the task more difficult are visual and auditory. The Virtual Class Task uses also mixed, visual-auditory distractors. This kind of stimuli allows to assess the selectivity, stability or divisibility of attention. The diagnosis with the use of virtual reality test provides relevant information about the cognitive functioning of the subjects. Additionally, this kind of assessment is very interesting for children which is one more advantage worth mentioning. The high ecological validity of results allows for creating an action plan focused on improving the functioning of children with attention-deficit/hyperactivity disorder.