Listening effort may be defined as the cognitive resources needed to understand an auditory message. A sustained requirement for listening effort is known to have a negative impact on individuals' sense of social connectedness, well-being and quality of life. A number of hearing-specific patient-reported outcome measures (PROMs) exist currently; however, none adequately assess listening effort as it is experienced in the listening situations of everyday life. The Listening Effort Questionnaire-Cochlear Implant (LEQ-CI) is a new, hearing-specific PROM designed to assess perceived listening effort as experienced by adult CI patients. It is the aim of this study to conduct the first psychometric evaluation of the LEQ-CI's measurement properties.This study is a phased, prospective, multi-site validation study in a UK population of adults with severe-profound sensorineural hearing loss who meet local candidacy criteria for CI. In phase 1, 250 CI patients from four National Health Service CI centres will self-complete a paper version of the LEQ-CI. Factor analysis will establish unidimensionality and Rasch analysis will evaluate item fit, differential item functioning, response scale ordering, targeting of persons and items, and reliability. Classical test theory methods will assess acceptability/data completeness, scaling assumptions, targeting and internal consistency reliability. Phase 1 results will inform refinements to the LEQ-CI. In phase 2, a new sample of adult CI patients (n=100) will self-complete the refined LEQ-CI, the Speech, Spatial and Qualities of Hearing Scale, the Nijmegen Cochlear Implant Questionnaire and the Fatigue Assessment Scale to assess construct validity.This study was approved by the Abertawe Bro Morgannwg University Health Board/Swansea University Joint Study Review Committee and the Newcastle and North Tyneside 2 Research Ethics Committee, Ref: 18/NE/0320. Dissemination will be in high-quality journals, conference presentations and SEH's doctoral dissertation.