Since the first implantation in July 2001, the intrathecal baclofen (ITB) therapy for patients with generalized spasticity has been used in Slovenia for 20 years. The aim of this retrospective study was to evaluate the rates of different complications, especially if catheter-related complications were less frequent after the introduction of the coated catheter type in February 2013, and the potential correlation between higher baclofen doses and the incidence of complications. We retrospectively collected data from all patients in the registry during the period from 3 July 2001 to 31 December 2021. Among 138 patients (48 females), 120 patients had the first ITB system implanted at the University Medical Centre Ljubljana. Forty-three complications were reported in 38 patients (27%), with a total complication rate of 0.203/1000 days or 0.074/pump year. The most frequent was catheter-related (0.083/1000 days or 0.030/pump year), followed by skin-related (0.063/1000 days or 0.023/pump year) and pump-related complication (0.026/1000 days or 0.009/pump year). The incidence of catheter-related complications decreased significantly since the use of Ascenda type catheter: 14/7 complications per 88/147 implantations (P = 0.008). Patients with complications had a statistically significantly higher dose of baclofen: median 400 µg/24h vs. median 300 µg/24h (P = 0.016). Our retrospective analysis confirmed a significant decrease of catheter-related complications after the implementation of Ascenda type catheter in February 2013. Patients with a higher ITB dose had a statistically significantly higher incidence of complications. The total complication rate was a bit higher as previously reported in other studies, which is consistent with a long follow-up time.