Exposure to secondhand smoke has consistently been linked to adverse health effects in children, including reduced lung function and various respiratory diseases. There is also increasing evidence that secondhand smoke exposure is associated with cognitive impairment and behavioral problems in children, This cross sectional study was done on 795 chiildren to determine the association between secondhand smoke exposure and peak expiratory flow rate (PEFR) and cognitive performance among the primary school children in Kota Bharu Kelantan. A questionnaire was used to obtain information on socio-demography and smoking status of the household. The PEER was measured using a child Mini Wright peak expiratory flow meter while cognitive performance was assessed by four subtests of Weschler Intelligence Scale For Children (WISC III). Data analysis was done using SPSS version 11. Children were classified as exposed to secondhand smoke when at least one househoH member smoked. There were 442 (55 .6%) children exposed to secondhand smoke at home. The mean (SD) PEFR for unexposed and exposed children were 266.18 (60.80) l/min and 266 .06 (57. 70) l/min respectively, The mean (SD) scores for Digit Span Forward, Digit Span Backward Coding and Arithmetic in unexposed chiMren were 6.84 (1.80), 4.Z7(1.68), 45.25 (9,99) and 8.04 (1.04) respectively. The mean (SD) scores for exposed children were 6.73 (1 .77). 4.07 (l .65), 45.1 I (1 I ,03) and 8.13 (1 .00) respectively. Multivariate analysis of variance showed no signincant dijference in the PEFR (p=O.816) and the cognitive scores between exposed and unexposed primary school children in Kota Bharu, Kelantan