Objective: The objective of the present study was to investigate the longitudinal performance on open-set word perception in Mandarin children with cochlear implants (CIs). Methods: Prospective cohort study. One hundred and five prelingually deaf children implanted with CIs participated in the study. The Standard-Chinese Version of Monosyllabic Lexical Neighborhood Test (LNT) and Multisyllabic Lexical Neighborhood Test (MLNT) were used as open-set word perception evaluation tools. Evaluations were administrated at 6, 12, 24, 36, 48, 60, 72, and 84 months post CI stimulation, respectively. Results: (1) Spoken word perception performance of congenitally deaf children with CIs improved significantly over time. (2) The fastest improvement occurred in the first 36 months after initial activation, then the improvement slowed down and the final peak score of 81.7% correct was achieved at 72 months after initial activation. (3) Early implanted children exhibited better longitudinal performance. (4) Lexical factors affected consistently in each evaluation session. For lexically harder words, such as monosyllabic hard words, there was substantial room for improvement even after long-term use of CI. Conclusions: (1) CI continuously provided significant benefits in word perception to children with severe/profound sensorineural hearing loss. (2) Age at implantation and Mandarin lexical factor affected longitudinal performance significantly. (C) 2015 Elsevier Ireland Ltd. All rights reserved.