Background: Epidural opioids are frequently combined with local anaesthetics for an additive antinociceptive effect. We investigated the efficacy of epidural fentanyl to 1.25 or 1.5 mg/ml ropivacaine for post‐operative epidural analgesia in children.Methods: One hundred and eight children undergoing hypospadias repair were randomized to receive 1.25 mg/ml ropivacaine (R1.25 group), 1.25 mg/ml ropivacaine with 0.2 mcg/kg/h of fentanyl (R1.25F group), 1.5 mg/ml ropivacaine (R1.5 group) or 1.5 mg/ml ropivacaine with 0.2 mcg/kg/h of fentanyl (R1.5F group) for post‐operative epidural analgesia. The epidural catheter was threaded caudally through the L4‐5 interspace. The face, legs, activity, cry, consolability (FLACC) score was assessed at every hour and at FLACC score >4, an epidural bolus of 0.5 ml/kg of ropivacaine 1.5 mg/ml was given as the rescue analgesia. The incidence of side effects such as hypoxia, sedation, pruritus, nausea and/or vomiting was recorded.Results: The need for rescue analgesia was higher in the R1.25 group compared with that in the other three groups (all P<0.05). The incidence of side effects was higher in the R1.5F group compared with that in the R1.25 and R1.5 groups (both P=0.010).Conclusion: The addition of 0.2 mcg/kg/h fentanyl to 1.5 mg/ml ropivacaine increased the incidence of side effects without improvement of analgesia in infants and children undergoing hypospadias repair. The use of plain 1.25 mg/ml ropivacaine increased the need for rescue analgesia and this could be compensated by addition of fentanyl.