Background: Previously, the RICAT (Reduction of Inappropriate use of intravenous and urinary CATheters) study had been conducted by ourselves to reduce inappropriate use of intravenous and urinary catheters in medical wards to prevent healthcare-associated infections. Aim: To compare surgical and medical wards, and to determine risk factors for inappropriate catheter use. Methods: A cross-sectional study was performed from October, 2017, to May, 2018, in surgical wards of two university hospitals in the Netherlands. Patients were prospectively observed every other week for seven months. Inappropriate use was compared with non-surgical wards in the RICAT study. Findings: In all, 409 surgical patients were included, and they were compared with 1781 medical patients. Inappropriate use occurred in 36 (8.5%) out of 425 peripheral intravenous catheters in 373 surgical patients, compared to 400 (22.9%) out of 1747 peripheral intravenous catheters in 1665 medical patients, a difference of 14.4% (95% confidence interval (CI): 11.1–17.8; P < 0.001). Inappropriate use of urinary catheters occurred in 14 (10.4%) out of 134 surgical patients, compared to 105 (32.4%) out of 324 medical patients, a difference of 22.0% (95% CI: 14.7–29.2; P < 0.001). Subgroup analysis in the two university hospitals confirmed these differences. The main risk factor for inappropriate use of peripheral intravenous catheters was admission in medical wards (odds ratio (OR): 3.50; 95% CI: 2.15–5.69), which was also one of the main risk factors for urinary catheters (OR: 2.75; 95% CI: 1.36–5.55). Conclusion: Inappropriate use of catheters is more common in medical wards compared to surgical wards. Prevention strategies to reduce healthcare-associated infections should primarily focus on sites with high prevalence of inappropriate use.