Whether posterior lumbar interbody fusion (PLIF) is effective in patients older than 55 years remains questionable because of the high prevalence of adjacent segment disease. We retrospectively investigated early clinical outcomes and radiological changes at upper adjacent disc (UAD) level in such age-group patients who underwent advanced dynamic stabilization (ADS) or PLIF. ADS or PLIF were performed in patients with grade 1 spondylolisthesis or disc degeneration complicated by apparent vacuum phenomenon. All patients suffered from neurological symptoms in lower limbs with/without low back pain. In all, 16 patients (six females; mean age, 69.0 ± 8.5 years) who underwent ADS and 14 patients (seven females; mean age, 67.8 ± 9.3 years) who underwent PLIF were followed-up, and preoperative and postoperative final disc height (DH) and range of motion (ROM) were investigated retrospectively using dynamic radiography at the operated and UAD levels. Clinical data of patients who underwent ADS and PLIF were as follows: postoperative follow-up, 459.3 ± 263.5 and 507.7 ± 288.3 days; preoperative Japanese Orthopaedic Association (JOA) score, 14.4 ± 4.1 and 13.4 ± 4.5; and recovery rate of JOA score, 67.5 ± 18.5 and 50.1 ± 23.4%, respectively. Recovery rate of JOA score in ADS group was significantly high compared to PLIF group (P = 0.044). At UAD level, ROM decreased from 4.7 ± 2.9° preoperatively to 3.6 ± 2.6° postoperatively in the ADS group and increased from 3.4 ± 4.1° preoperatively to 5.6 ± 2.8° postoperatively with significant hypermobility (P = 0.020) in the PLIF group. ADS has the advantage in clinical outcomes even in the postoperative early stage, avoiding the early hypermobility at UAD level, compared to PLIF in patients older than 55 years.