IntroductionHemispheric asymmetry of the central nervous system affects various features of the brain involved in cognitive ability. Functional asymmetry, such as different hearing ability in the left or right ear, will also affect cognitive processes.Material and methodsThe aim of this study was to assess how intelligence measures and cognitive abilities in children and adolescents might have been affected by hearing deficits in the left or right ear. The study involved 208 children, 126 who were in an experimental group and 82 in a control group. In the experimental group, there were 26 children who were diagnosed with right-sided hearing loss, 34 with leftsided hearing loss, and 66 with bilateral hearing loss; all children in this group had used hearing devices since diagnosis. We assessed hearing unilaterally and bilaterally and looked for asymmetries in terms of intelligence measures and visual and spatial functioning.ResultsChildren with bilateral hearing impairment had lower intelligence compared to those without impairment. Children with unilateral hearing impairment had similar intelligence level compared to well hearing children. Children with left-sided hearing impairment had higher intelligence compared to those with right-sided hearing impairment and lower nonverbal intelligence compared to well-hearing children. Children with right-sided hearing impairment had lower verbal intelligence.ConclusionsHearing impairment has an impact on various measures of intelligence, as well as on the organisation and performance of cognitive processes.