The aim of the study was to assess whether heart rate (HR) monitoring is suitable to estimate energy expenditure in spastic cerebral palsied (CP) children, who are known to have very low levels of daily physical activity. Total daily energy expenditure (TEE) predicted from HR recording(TEEHR, measured over 2 or 3 d) was therefore compared with TEE measured by doubly labeled water (TEEDLW, measured over 14 d) in nine children with spastic diplegia/tetraplegia (mean ± SD age 10.7 ± 1.6 yr). At group level, there was no difference in TEEDLW (7.4± 2.1 MJ·d-1) and TEEHR (7.4 ± 2.2 MJ·d-1). Spearman correlation between both methods was 0.88(P < 0.001). Individual estimates of TEEHR ranged from-16.9% to +20.0%, with five TEEHR values within ± 10% of TEEDLW. It was concluded that also in children with low levels of daily physical activity, HR monitoring (preferably 3 sampling days) can provide a close group estimate of energy expenditure. At the individual level, the method is not suitable.