In this thesis the intricacies of service user and staff perceptions of psychological interventions for mental health difficulties were explored. Expanding upon this theme, mothers and staff on a Mother and Baby Unit (MBU) were asked about their views regarding the acceptability and feasibility of the implementation of a parenting intervention, Baby Triple P Positive Parenting Programme (Baby TP). This investigation is presented as four papers: a literature review, two empirical papers (a & b) and, a critical review and personal reflection of the research process.The literature review, a meta-synthesis of qualitative studies, explores service user and staff perceptions of psychological interventions for mental health difficulties. Twenty-eight studies were synthesised to develop comprehensive understanding of subtle, specific and overlapping elements involved in the implementation of psychological intervention. Guided by Noblit and Hare's (1988) approach, 11 over-arching themes and 25 sub-ordinate themes emerged from the synthesis. Findings provide a detailed description of the concepts pertinent to both service users and staff. Implications are identified for service managers and clinicians in obtaining optimum efficiency and outcomes of psychological intervention. The empirical study is a Q-methodological investigation into service user and staff perceptions of the acceptability and feasibility of a parenting intervention, Baby TP, on a MBU. This study is split into two population-specific papers. Overall five main factors were identified (service users: three; staff: two), which provides new insights into the acceptable and feasible elements of a parenting intervention within this specialist setting. The findings highlight a positive consensus as to the acceptability and feasibility of Baby TP in a MBU setting alongside a number of identified needs pertinent to service users, staff and the setting. Clinical implications and recommendations are provided to address identified areas of need for both populations within this setting. The third paper is a critical review of the thesis illustrated through personal reflections of the research process.