Patient-orientated questionnaires are becoming increasingly popular in the assessment of outcome and are considered to provide a less biased assessment of the surgical result than traditional surgeon-based ratings. The present study sought to quantify the level of agreement between patients' and doctors' global outcome ratings after spine surgery. 1,113 German-speaking patients (59.0 +/- 16.6 years; 643 F, 470 M) who had undergone spine surgery rated the global outcome of the operation 3 months later, using a 5-point scale: operation helped a lot, helped, helped only little, didn't help, made things worse. They also rated pain, function, quality-of-life and disability, using the Core Outcome Measures Index (COMI), and their satisfaction with treatment (5-point scale). The surgeon completed a SSE Spine Tango Follow-up form, blind to the patient's evaluation, rating the outcome with the McNab criteria as excellent, good, fair, and poor. The data were compared, in terms of (1) the correlation between surgeons' and patients' ratings and (2) the proportions of identical ratings, where the doctor's "excellent" was considered equivalent to the patient's "operation helped a lot", "good" to "operation helped", "fair" to "operation helped only little" and "poor" to "operation didn't help/made things worse". There was a significant correlation (Spearman Rho = 0.57, p < 0.0001) between the surgeons' and patients' ratings. Their ratings were identical in 51.2% of the cases; the surgeon gave better ratings than the patient ("overrated") in 25.6% cases and worse ratings ("underrated") in 23.2% cases. There were significant differences between the six surgeons in the degree to which their ratings matched those of the patients, with senior surgeons "overrating" significantly more often than junior surgeons (p < 0.001). "Overrating" was significantly more prevalent for patients with a poor self-rated outcome (measured as global outcome, COMI score, or satisfaction with treatment; each p < 0.001). In a multivariate model controlling for age and gender, "low satisfaction with treatment" and "being a senior surgeon" were the most significant unique predictors of surgeon "overrating" (p < 0.0001; adjusted R (2) = 0.21). Factors with no unique significant influence included comorbidity (ASA score), first time versus repeat surgery, one-level versus multilevel surgery. In conclusion, approximately half of the patient's perceptions of outcome after spine surgery were identical to those of the surgeon. Generally, where discrepancies arose, there was a tendency for the surgeon to be slightly more optimistic than the patient, and more so in relation to patients who themselves declared a poor outcome. This highlights the potential bias in outcome studies that rely solely on surgeon ratings of outcome and indicates the importance of collecting data from both the patient and the surgeon, in order to provide a balanced view of the outcome of spine surgery.