One hundred twenty-two patients with cervical spon- dylotic myelopathy (CSM) or ossification of the posterior longitudinal ligament (OPLL) were randomized to C3 laminectomy + C4–C6 laminoplasty (LN; n=61) or C3–C6 laminoplasty (LP; n=61); modified intention-to-treat included 109 (LN n=51; LP n=58). The primary outcomes were C2–C7 Cobb angle (CA) and Neck Disability Index (NDI). Secondary outcomes included segmental CA (C2–C3, C4–C7), cervical SVA, T1 slope and T1S–CL, C2–C3 interlaminar fusion, EQ-5D, and NRS pain. Outcomes were assessed up to 3 years. Overall, the results revealed no between-group difference in C2–C7 CA, but worse NDI and EQ-5D in the LN group, greater proximal (C2–C3) lordosis with less distal (C4–C7) lordosis, larger cSVA at 2–3 years, and a higher prevalence of an “S-curve” (proximal lordosis/distal kyphosis) pattern associated with poorer clinical outcomes. These findings suggest adding C3 laminectomy does not prevent kyphosis overall and may be linked to unbalanced alignment and inferior patient-reported outcomes.