BACKGROUND: In patients with colorectal liver metastases (CRLM) preoperative imaging may include contrast-enhanced (ce) MRI and [18 F]fluorodeoxyglucose (18 F-FDG) PET-CT. This study assessed trends and variation between hospitals and oncological networks in the use of preoperative imaging in the Netherlands. METHODS: Data for all patients who underwent liver resection for CRLM in the Netherlands between 2014 and 2018 were retrieved from a nationwide auditing database. Multivariable logistic regression analysis was used to assess use of ceMRI, 18 F-FDG PET-CT and combined ceMRI and 18 F-FDG PET-CT, and trends in preoperative imaging and hospital and oncological network variation. RESULTS: A total of 4510 patients were included, of whom 1562 had ceMRI, 872 had 18 F-FDG PET-CT, and 1293 had combined ceMRI and 18 F-FDG PET-CT. Use of ceMRI increased over time (from 9·6 to 26·2 per cent; P < 0·001), use of 18 F-FDG PET-CT decreased (from 28·6 to 6·0 per cent; P < 0·001), and use of both ceMRI and 18 F-FDG PET-CT 16·9 per cent) remained stable. Unadjusted variation in the use of ceMRI, 18 F-FDG PET-CT, and combined ceMRI and 18 F-FDG PET-CT ranged from 5·6 to 100 per cent between hospitals. After case-mix correction, hospital and oncological network variation was found for all imaging modalities. DISCUSSION: Significant variation exists concerning the use of preoperative imaging for CRLM between hospitals and oncological networks in the Netherlands. The use of MRI is increasing, whereas that of 18 F-FDG PET-CT is decreasing.