BackgroundTo explore the clinical prognostic utility of the preoperative cholesterol-to-lymphocyte ratio (CLR) in outcomes for colorectal cancer liver metastasis (CRLM) patients receiving simultaneous resection of the primary lesion and liver metastases.MethodsA total of 444 CRLM patients receiving simultaneous resections were enrolled. The optimal cut-off value for CLR was determined using the highest Youden’s index. Patients were divided into the CLR < 3.06 group and the CLR≥3.06 group. Propensity score matching analysis (PSM) and the inverse probability of treatment weighting (IPTW) method were conducted to eliminate bias between the two groups. The outcomes included short-term outcomes and long-term outcomes. Kaplan–Meier curves and log-rank tests were used to analyse progression-free survival (PFS) and overall survival (OS).ResultsIn the short-term outcome analysis, after 1:1 PSM, 137 patients were distributed to the CLR < 3.06 group and CLR≥3.06 group. No significant difference was noted between the two groups (P> 0.1). Compared with patients with CLR < 3.06, patients with CLR≥3.06 had comparable operation times (320.0 [272.5–421.0] vs. 360.0 [292.5-434.5],P =0.088), blood loss (200.0 [100.0-400.0] vs. 200.0 [150.0-450.0],P= 0.831), postoperative complication rates (50.4% vs. 46.7%,P= 0.546) and postoperative ICU rates (5.8% vs. 11.7%,P =0.087). In the long-term outcome analysis, Kaplan–Meier analysis showed that compared with patients with CLR < 3.06, patients with CLR≥3.06 had worse PFS (P= 0.005, median: 10.2 months vs. 13.0 months) and OS (P= 0.002, median: 41.0 months vs. 70.9 months). IPTW-adjusted Kaplan–Meier analysis showed that the CLR≥3.06 group had worse PFS (P= 0.027) and OS (P= 0.010) than the CLR < 3.06 group. In the IPTW-adjusted Cox proportional hazards regression analysis, CLR≥3.06 was an independent factor for PFS (HR = 1.376, 95% CI 1.097–1.726,P =0.006) and OS (HR = 1.723, 95% CI 1.218–2.439,P= 0.002). IPTW-adjusted Cox proportional hazards regression analysis including postoperative complications, operation time, intraoperative blood loss, intraoperative blood transfusion and postoperative chemotherapy revealed that CLR≥3.06 was an independent factor for PFS (HR = 1.617, 95% CI 1.252–2.090,P <0.001) and OS (HR = 1.823, 95% CI 1.258–2.643,P= 0.002).ConclusionsThe preoperative CLR level predicts unfavourable outcomes in CRLM patients receiving simultaneous resection of the primary lesion and liver metastases and should be taken into consideration when developing treatment and monitoring strategies.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12893-023-01988-7.