Purpose <p>Cervical Radicular Syndrome is predominantly treated conservatively, but surgical treatment can be considered after shared decision-making. Knowledge about difference in outcome is scarce. The CASINO trial aims to enhance this knowledge to assist patients and physicians in optimizing treatment choices.</p> Methods <p>A multi-centre observational cohort study was conducted in patients visiting a neurologist or neurosurgeon with CRS and disc-herniation. Conservative and surgical treatment were discussed and in agreement a decision was made. 141 patients with cervical radiculopathy due to intervertebral disc herniations were included, 88 were surgically and 53 were conservatively treated. Visual Analogue Scale for arm pain and Neck Disability Index served as primary outcome parameters. Secondary outcome measures involved VAS neck pain and the EuroQol VAS. Data were collected at baseline, 6, 12, 26, 38, 52 and 104 weeks after inclusion, and analysed using linear mixed-effects models.</p> Results <p>At baseline, the surgical treatment-arm had more arm pain (VAS Arm Pain, <i>p</i> =.017) but other baseline parameters were comparable. However, during the two years follow up period the surgical arm fared better than the conservatively treated patients: VAS arm pain decreased 12&#xa0;mm more in the surgical group than in the conservative group (<i>p</i> =.053), exceeding the Minimal Clinical Important Difference (MCID). VAS neck pain decreased 19&#xa0;mm more in the surgical group than in the conservative group (<i>p</i> =.002), illustrating a significant and clinically relevant difference between the treatment arms.</p> Conclusion <p>During two years follow up, differences could be substantiated between the two treatment arms regarding arm and neck pain.</p>