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99mTc-EDDA/HYNIC-TOC is an easily available and cheaper radionuclide that could be used for somatostatin-receptor-based imaging of neuroendocrine tumours (NETs). We aimed to evaluate the diagnostic performance of 99m Tc-EDDA/HYNIC-TOC compared to 111 In-DTPA-octreotide in patients (pts) with NETs. We performed a prospective diagnostic study including pts with biopsy-confirmed NET and at least one visible lesion at conventional imaging. Two independent nuclear medicine physicians evaluated pts who underwent 99m Tc and 111 In scans and images. The primary outcome was comparative diagnostic accuracy of 99m Tc and 111 In. Secondary outcomes include safety.Nine pts were included and performed 14 paired scans. Overall, 126 lesions were identified. 99m Tc demonstrated superior sensitivity both when all images were analysed (93.7, 95% CI 88.1% -96.8% versus 74.8%, 95% CI 66.6 -81.6%, p < 0.001) and when liverspecific images were analysed (97.8%, 95% CI 92.7% -99.5% versus 85.1%, 95% CI 76.6% -91.0%, p < 0.001). 99m Tc was also associated with a lower negative likelihood ratio (LR) (0.002, 95% CI 0.009 -0.1 versus 0.19, 95% CI 0.12 -0.42, p = 0.009) when evaluating hepatic lesions. Adverse events happened in 3 pts after 111 In and in 2 pts after 99m Tc, all grade 1. The 99m Tc demonstrated a higher sensitivity overall and a better negative LR in liver-specific images compared to 111 In in pts with NETs. Our findings suggest that 99m Tc is an alternative to 111 In and is especially useful in ruling out liver metastases. NCT02691078.