To investigate intrasession and intersession reliability of balance tests in children with or without disabilities, 50 children without disabilities (ND) and 36 children with cerebral palsy (CP) aged from 5 to 12 years were tested. Intrasession reliability of postural stability of the Smart Balance Master System and one-leg standing test were assessed in both groups and intersession reliability of the Smart Balance Master System and balance subtest of the Bruininks-Oseretsky Test of Motor Proficiency (BOTMP) were assessed in ND children. Intersession reliability of the postural stability test in ND children, obtained using the Smart Balance Master System, was of moderate to good reliability in centre target (CT), sway vision (SV), eyes open and sway surface (EOSS), and sway vision and sway surface (SVSS; ICC 0.72 to 0.84). In children with CP, intrasession reliability was high in CT (ICC 1). One-leg standing tests in both groups also had moderate to good intersession reliability (ICC 0.56 to 0.99). Agreement of failure score of lateral rhythmic shifting (LRS) at 1 second and 2 seconds pace was 85% and 93% respectively in ND children. Within the balance subtest of BOTMP, only two items had 100% agreement. Results suggest that postural stability tests in four conditions (CT, SV, EOSS, and SVSS), LRS, one-leg standing, and walking on a line are reliable and can be used to monitor balance control in ND children. Postural stability in CT condition and one-leg standing test are reliable in children with CP. Further study is needed to establish more reliable balance tests for children with CP.