PURPOSE: To compare the outcomes of expansive open-door laminoplasty with instrumented fusion (ELIF) and expansive open-door laminoplasty with instrumented non-fusion (ELINF) for multilevel cervical ossification of the posterior longitudinal ligament (OPLL). METHODS: Patients who underwent ELIF or ELINF due to multilevel cervical OPLL from June 2013 to June 2019 were identified. Clinical and radiological outcomes were compared between the two groups. RESULTS: A total of 78 patients were enrolled in this study with a minimum follow-up of 24 months, including 42 patients in the ELIF group and 36 patients in the ELINF group. At the final follow-up, sagittal vertical axis (SVA) and C2-C7 Cobb angle in the ELIF group were significantly better than those in the ELINF group, and cervical range of movement (ROM) in the ELIF group decreased significantly than that in the ELINF group. The incidence of OPLL progression at the final follow-up was 4.76% (2/42) in the ELIF group and 27.78% (10/36) in the ELINF group. Postoperative Japanese Orthopaedic Association (JOA) score, neck disability index (NDI), and visual analog scale (VAS) score improved significantly in each group, but JOA score and recovery rate (RR) in the ELIF group were significantly better than those in the ELINF group at the final follow-up. When K-line was positive, the difference in the final JOA score between the two groups was not significant, but the RR in the ELIF group was significantly better than that in the ELINF group. When K-line was negative, the final JOA score and RR in the ELIF group were significant higher than those in the ELINF group. CONCLUSIONS: ELIF and ELINF were two effective surgical procedures for treating multilevel cervical OPLL. However, ELIF was superior to ELINF due to better postoperative JOA score and RR, significant improvement of C2-C7 Cobb angle and maintenance of SVA, and suppressant effect on OPLL progression, especially for patients with K-line ( - ) OPLL.