Conclusion: Performance in consonant-vowel (CV) monosyllable speech perception after cochlear implantation (CI) in the elderly (>= 65 years) is equivalent to that of young adults (18-64 years). Present data in the Japanese language supported the indication for CI in the elderly. Word recognition after CI was significantly lower in the elderly than young adults. Objective: This study compared outcomes of monosyllable perception and word recognition after CI between elderly patients and young adults with post-lingual deafness. Age-related differences in CV monosyllable speech perception in Japanese were examined. Methods: A retrospective chart review of 137 patients with post-lingual deafness who underwent CI at Okayama University Hospital during 1992-2014 [young adults aged 18-64 years (n = 96) and elderly aged >= 65 years (n = 41) at implantation] was conducted. CV monosyllable speech perception post-CI was compared among age groups (18-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89). CV monosyllable perception and word recognition scores post-CI were compared between the elderly and young adults. Results: There was no significant difference in CV monosyllable speech perception among age groups. CV monosyllable speech perception in the elderly (61.4 +/- 25.5%) did not differ from that of young adults (65.9 +/- 24.8%). Word recognition scores were significantly lower in the elderly (64.3 +/- 28.1%) than young adults (80.4 +/- 25.9%) (p < 0.05).