To date there has been little research on family changes caused by having a child of 0 to 7 years old with autism in the family. This thesis examines the diagnosis of autism spectrum disorder (ASD) in the context of the family and compared families' experiences in Ireland and Romania. This research took a family system perspective, exploring how families with children on the autism spectrum function during the particularly stressful period of the diagnosis process and thereafter. This Ph.D. thesis contains the results of a comparative study of Irish and Romanian families of children with ASD. The analysis of the similarities and differences of how families who are raising a child with autism function during the diagnostic process is expected to provide a better understanding of the overall experience of families and to improve sensitivity during the diagnostic process. Fifty-four families and their children were recruited from two institutions: 24 families from Ireland (Dublin, Cherry Orchard Hospital) and 30 families from Romania (Timisoara, Cas a Faenza). The children were aged between 2 and 7 years. During the process of data collection, a relatively large number of Irish families refused to participate in this research, or accepted the invitation initially and then later refused it or stated that they are very 'busy'. A total number of 77 Irish families were contacted by the researcher and asked to participate in this study. Only 24 families agreed to participate and 53 refused to participate. In contrast, all of the 30 Romanian families who were contacted and asked to participate in this research accepted. This comparative research study is unique as no previous studies have focused on the impact of ASD diagnostic on family systems across two cultures in Europe. The results showed that families of a child with ASD in Ireland had different experiences during the diagnostic process of their child, compared to the Romanian families. Differences were also found between the two groups with regard to the role of mother and father in raising a child with ASD, parents' worries when received the diagnosis, parents' awareness/knowledge about ASD, and parents' level of involvement. A semi-structured interview was used to analyse similarities and differences between the two groups. The duration of the diagnostic process was significantly different between the two countries. Aspects of family functioning were tested using the family adaptability and cohesion evaluation scale IV (FACES IV) (Olson et aI., 2010). The results showed similarities and differences between the two groups in terms of mean scores for family cohesion, flexibility, communication and satisfaction. Present findings should be used by policymakers in improving parent's accessibility to ASD services for their children (diagnostic and post-diagnostic) in both countries. There is a crucial need to develop specialized services for children with ASD. The findings indicate that both instruments used (semi structured interview and FACES IV) provided valuable information about family functioning and family experience during the diagnostic process. The limitations of the study were discussed.