Pediatric Evaluation of Disability Inventory (PEDI) is an instrument for evaluating function in children with disabilities aged 6 months to 7.5 years. The PEDI measures both functional performance and capability in three domains: (1) self-care, (2) mobility, and (3) social function. The PEDI has recently been translated into Norwegian. The purpose of this study was to investigate the inter-rater, inter-respondent and intra-rater reliability of the Norwegian version of the PEDI. Reliability was investigated in a sample of 30 Norwegian children without disabilities between 1.0 and 5.0 years. Interviews with parents were conducted twice by the same occupational therapist, and once by a physiotherapist. Kindergarten teachers were also interviewed by the occupational therapist. Using children without disabilities allows us to set up a standard for functional ability. Deviation from the point may indicate improvement or worsening of the state. The inter-rater and intra-rater part of the study showed excellent agreement of the observations, indicated both by small differences and high Intraclass Correlation Coefficients (ICC) (0.95-0.99). The discrepancy between the different interviews was highest between the reports from the parents and the kindergarten teachers (inter-respondent reliability), indicated by ICC from 0.64-0.74. Results of this study indicate that improved reliability is secured when the same interviewer interviews the same respondent, as well as when two trained interviewers interview the same respondent. The consistency of scores should be reviewed when different respondents are interviewed. Professionals administering the PEDI needs to be trained following a required procedure in order to secure consistency in their rating.