The process of transition from Child and Adolescent Mental Health Services to Adult Mental Health Services cannot be defined only as a process of transfer from one service to another, but as an intentional and planned process, meeting the medical, psychosocial and educational needs of patients. According to descriptions from various countries, the transition process currently lacks careful planning and execution, being experienced as an abrupt process by patients and multiple people involved in their care. This paper reflects upon transition practices in mental health services, summarising the current literature and presenting two Portuguese mental health transition projects, as examples of how the process of transition might be improved. Poorly planned transitions may contribute to an increased risk of non-adherence to treatment, loss to follow-up, and poorer health outcomes, as well as significant economic costs. Despite some general guidelines on this topic, transition protocols, if available, vary significantly across countries and regions, and no current existing model appears to fully meet the identified needs of patients in transition. In Portugal, the Semente Program in Hospital Prof. Doutor Fernando Fonseca intends to identify and intervene in the care of children of adult patients with mental health issues. The Shared Service for Teens and Young Adults, a collaboration between Centro Hospitalar Psiquiátrico de Lisboa and Hospital Dona Estefânia, incorporates some of the recommendations summarised in this paper. Better understanding and development of communication pathways, continuity, coordination of care, referral protocols, and service delivery might contribute to a more robust design of transitional mental health care, thus making it more accessible, acceptable and efficient.