The aim of the study was to explore particular challenges faced when designing virtual environments for children with autism, with the purpose of training social skills. Our findings are based on studying autistic behavior during three years (primary and secondary sources), analysis of related system and other computer mediated assistive technology, as well as general game design. From these studies, we have identified eight critical design parameters that must be adjustable in a system suitable for autistic persons. The importance of the parameters, their variation range, as well as the need for independent adjustment of these were estimated and verified by experienced expert pedagogues. Copyright © Freund Publishing House Limited.