Dyssynergic defecation, defined as the incoordination of rectoanal and abdominal muscles and the pelvic floor which are necessary for the appropriate relaxation, is characterized by paradoxical anal contraction, inadequate anal relaxation, or abnormal rectal propulsion; it is considered a cause of refractory primary constipation. The prevalence of dyssynergic defecation in the pediatric age is still little known. The studies that have evaluated the defecation dynamics through anorectal manometry suggest that 36.8% to 80.9% of children with functional constipation (FC) present dyssynergic defecation. High-resolution Anorectal Manometry (HRAM) is a tool for the evaluation of the sensitivity and defecation dynamics; it allows to establish the diagnosis of dyssynergia and its classification. The objective of this study was to determine the prevalence of dyssynergic defecation in children with FC and characterize the most common type of dyssynergia evaluated through a HRAM. In this study, 63 files of pediatric patients with FC diagnoses were included. Of these, 41.3% (n=26) were female and 58.7% (n=37) were male. The median age in the group of dyssynergia was 8 years, while for the FC group it was 9 years; the distribution by sex was similar. Of the included patients, 41.3% (n=26) showed dyssynergic defecation, and 58.7% (n=37) showed normal anorectal manometry. Regarding the type, 84.6% (n=22) were of type I, 7.7% (n=2) was the percentage for both types III and IV, and no patients were reported for type II.