The 26-item WHOQOL-BREF is the brief version of a multi-faceted, patient-reported, cross-cultural health-related quality of life (HRQoL) survey developed by the World Health Organization (WHO) that assesses generic quality of life (QoL) issues commonly impacted by health problems. This thesis outlines how a two-phased exploratory sequential mixed-methods study identified seven items for a mental health recovery module to improve the precision of the WHOQOL-BREF to measure mental-health-related QoL (MHRQoL) by adding personal recovery determinants that affect the QoL of people with mental health issues. A qualitative phase (Phase 1) invited 88 participants to discuss how QoL is changed by mental health issues and during recovery from mental health problems. Coders identified potential MHRQoL themes from the recorded group and interview discussions with participants with lived experience (LE) of mental health issues and recovery supporters. Results were rank-ordered after summative frequency analysis and then triangulated against LE participant-rated importance data to identify 24 personal recovery determinants that more frequently affected QoL. A question writing team evaluated these 24 determinants and wrote candidate items that reflected LE participant experiences in the WHOQOL question format. Questions were then placed at relevant points within a 55-item research survey comprising of 26 WHOQOL-BREF items, 5 New Zealand (NZ) national items, and 24 Phase 1 candidate items. Finally, a pilot group of LE volunteers reviewed the comprehensibility and relevance of the survey items, survey time and cognitive burden, prior to the survey’s use in Phase 2. A quantitative phase (Phase 2) invited participants with and without mental health or addiction issues to complete the Phase 2 research survey. The 667 surveys that met inclusion criteria comprised of 389 surveys from LE participants and 278 surveys from comparison group participants. An established set of classical test theory (CTT) and Rasch criteria, previously developed to identify NZ items for the WHOQOL, were used in Phase 2 to identify the final items for the MHRQoL module. CTT analysis established that, other than the spirituality item, 23 out of 24 candidate items differentiated between the comparison group and LE participants. Seventeen candidate items: (1) did not duplicate existing WHOQOL-BREF, NZ national items, or candidate MHRQoL items; and (2) correlated with specified MHRQoL construct variables. These 17 items were reduced to seven items through 12 steps of iterative partial-credit Rasch analyses. Items misfitting against established item response theory (IRT) criteria were progressively eliminated. The final seven items that met Rasch's unidimensional model fit requirements enquired about (1) believing in recovery; (2) recognising strengths; (3) self-awareness; (4) acceptance; (5) relating to others; (6) feeling understood; and (7) recovery progress. Ordinal-to-interval scale conversion tables are provided to optimise measurement precision. Seven MHRQoL items were identified for an adjunct MHRQoL module to be used with the WHOQOL-BREF. The WHOQOL-BREF with adjunct MHRQoL module can be used in research applications as a patient-reported outcome measure (PROM) to support a service’s aim to be recovery orientated, to assess the effect of interventions on QoL, and to support people with mental health issues to improve their QoL.