The Juvenile Arthritis Multidimensional Assessment Report (JAMAR) is a new parent/patient reported outcome measure that enables a thorough assessment of the disease status in children with juvenile idiopathic arthritis (JIA). We report the results of the cross-cultural adaptation and validation of the parent and patient versions of the JAMAR in the Canadian varieties of English and French. The reading comprehension of the questionnaires were tested in a probe sample of ten parents and ten JIA patients for Canadian English and other ten parents and ten JIA patients for Canadian French. Each participating centre was asked to collect demographic, clinical data and the JAMAR in 100 consecutive JIA patients or all consecutive patients seen in a 6-month period and to administer the JAMAR to 100 healthy children and their parents. The statistical validation phase explored descriptive statistics and the psychometric issues of the JAMAR: the 3 Likert assumptions, floor/ceiling effects, internal consistency, Cronbach's alpha, interscale correlations, test-retest reliability and construct validity (convergent and discriminant validity). A total of 208 JIA patients (2.9% systemic, 41.8% oligoarticular, 27.9% RF negative polyarthritis, 27.4% other categories) and 152 healthy children, were enrolled at two paediatric rheumatology centres. The JAMAR components discriminated well healthy subjects from JIA patients. Notably, there was no significant difference between the healthy subjects and their affected peers in the psychosocial quality of life variable. All JAMAR components revealed good psychometric performances. In conclusion, the Canadian English and French versions of the JAMAR are valid tools for the assessment of children with JIA and are suitable for use both in routine clinical practice and clinical research.