Chewing disorders can be seen in children with neuromuscular diseases (NMDs), which may cause swallowing difficulties such as choking, retching and food stuck feeling in the throat. Due to these effects, it is important to determine chewing disorders early with appropriate assessment methods to plan appropriate therapies in NMDs. The aim of this study was to investigate reliability and validity of the Karaduman Chewing Performance Scale (KCPS) in children with NMDs. Age, sex and diagnosis were recorded. Children were asked to chew a standardised biscuit while video-recording. Two physical therapists scored each video according to the KCPS. The correlation between the KCPS scores of 2 therapists was analysed for interobserver reliability. One therapist rescored the recordings after an interval of 2weeks for intra-observer reliability. The Pediatric Version of the Eating Assessment Tool (PEDI-EAT-10) was used for criterion-based validity. Sixty-eight children with a mean age of 8.34 +/- 3.73 (min=2.5, max=14.5) years were included, of which 94.1% were male. Karaduman Chewing Performance Scale scores were found to be level 0 in 20 cases, level 1 in 35 cases, level 2 in 12 cases and level 3 in 1 case. A positive, very strong correlation was detected between 2 therapists (r=.93, P<.001) and between 2 examinations of 1 therapist (r=.83, P<.001). A good correlation between the KCPS and PEDI-EAT-10 was detected (r=.62, P<.001). Chewing function, especially food processing phase, deteriorated in children with NMDs. The KCPS could be used as a reliable and valid instrument in determining chewing performance level for children with NMDs.