Outcome measures for adult cochlear implant (CI) users are needed to evaluate music rehabilitation tools. Music questionnaires developed for CI users may capture real-world music experiences better than music perception tests but have not been designed to measure outcomes. A new reliable and valid instrument measuring a wide range of music experiences and the impact of music on the quality of life (QOL) of adult CI users could be more appropriate for the assessment of music rehabilitation. This PhD thesis made steps towards the development of such a measure. Music-related Quality of Life (MRQOL) was defined as a function of music experiences and their importance in life. On the basis of this concept, two initial pools of questionnaire items were developed, one assessing musical abilities, attitudes and activities and another one assessing their importance. The items were generated using focus group data from 30 adult CI users and reviewed by 24 professionals for face validity and refinement. After completion of both sets of questions by 147 adult CI users, 18 items were selected for each set with the use of traditional psychometric techniques. The items grouped together into two meaningful domains (perception and engagement) with high reliability and some evidence for construct validity. Scores of ‘music perception and engagement’ and importance for the 18 items can be combined to measure the impact of music on QOL. The meaning of individual ‘impact’ scores and the ability of the questionnaire to measure changes have to be further studied. This thesis broadens the understanding of CI users’ relationship with music and the effects of music on their QOL. Novel aspects of music experience were identified. The MRQOL measure has the potential to become a standard measure of music-specific outcomes and of the impact of music on the QOL of adult CI users and hearing-impaired adults in general, with potential clinical utility.