Purpose: Previous studies have shown that the underlying pathophysiologic mechanism in children with breath holding may be generalised autonomic dysregulation. Thus, we performed cardiac rhythm and heart rate variability analyses using 24-hour Holter monitoring to evaluate the cardiac effects of autonomic dysregulation in children with breath-holding spells. Methods: We performed cardiac rhythm and heart rate analyses using 24-hour Holter monitors to evaluate the cardiac effects of autonomic dysregulation in children during a breath-holding spell. Our study group consisted of 68 children with breath-holding spells – 56 cyanotic type and 12 pallid type – and 39 healthy controls. Results: Clinical and heart rate variability results were compared between each spell type – cyanotic or pallid – and the control group; significant differences (p<0.05) in standard deviation of all NN intervals, mean of the standard deviations of all NN intervals for all 5-minute segments, percentage of differences between adjacent RR intervals >50 ms, and square root of the mean of the sum of squares of the differences between adjacent NN intervals values were found between the pallid and cyanotic groups. Conclusions: Holter monitoring for 24 hours and heart rate variability parameters, particularly in children with pallid spells, are crucial for evaluation of cardiac rhythm changes.