Children and adolescents with cognitive and developmental difficulties show difficulty in social interaction, feelings of rejection, autonomy, social rules and in behavioural and emotional self-regulation. Importantly, their subjective well-being is associated to social support and personal factors, such as self-esteem and a positive self-image. The data were collected in 16 schools, 8 in the North Region and 8 in the Lisbon Region of Portugal. The sample is composed by 1181 young people of which 51.5% were female, with ages ranging between 8 and 17 years. From the sample, 2.6% had special educational needs (SEN), and 3% did not use the Portuguese language at home. 12.2% had been retained one grade or more. Three regression models were built. Model 1 establishes the association between having SEN, grade and subjective well-being. The final model with all variables showed that social and personal characteristics present a stronger explicative value on children and adolescents' subjective well-being. The model also showed that, when social and personal variables are included the association between being a student with SEN and well-being is not statistically significant. Research and intervention implications include the need to promote subjective well-being, social and personal skills and a positive development in children and adolescents with SEN.