Surgery for Baker's cysts in children is plagued by high recurrent rate after the operation. In this study, a modified surgical method is developed to avoid the recurrence. Between 1995 and 2002, nine symptomatic Baker's cysts were excised in nine children, including six boys and three girls with a mean age of 5.7 years, were reviewed retrospectively. The diagnosis and follow-up were confirmed by clinical and ultrasound investigation. The modified surgical technique features a step in which the orifice of the posterior joint capsule is closed tightly by the application of one purse-string non-absorbable suture, and augmented by the suturing of the gastronomies tendon onto the closed orifice of the knee-joint capsule. Then the affected knee is immobilized with long leg cast for 2 weeks. After a mean follow-up of 8.3 years (ranged from 5.6 years to 12.1 years), none of the cysts recurred. All the patients were free of symptoms and none complained of any cosmetic problems. While comparing the affected and the unaffected knee, neither limitation of motion nor difference of muscle power was found. From the results, the modified surgical method is considered effective to treat the symptomatic Baker's cyst in children and to avoid its recurrence.