In this paper the authors present the initial results of the study on Critical Factors involved with play for children with disabilities. The European project IROMEC (Interactive Robotic Social Mediators as Companions IST-2005-2.6.1), that began in November 2006, will investigate how robotic toys can become social mediators, encouraging children with disabilities to play and to interact. Some of these children are unable to play autonomously due to their impairment and/or disability. To help these children learn how to play, a wide range of knowledge and a variety of skills are needed: these are the IROMEC Critical Factors, which are designed to be implemented as a useful basis for developing guidelines for teachers and rehabilitation professionals who would like to introduce robotic toys and methodologies in their work.