Recent successes in monitoring and diagnosing a variety of tumors using Tc-99m-PEG4-E[ PEG4-c(RGDfK)]2 (Tc-99m-3PRGD2) single-photon emission computed tomography (SPECT) imaging encouraged us to expand the use of this tracer. This case-control study aimed to evaluate the feasibility of Tc-99m-3PRGD2 imaging for detecting choroidal melanoma (CM) and for monitoring tumor response to plaque brachytherapy (PB). Ten consecutive patients with CM who underwent Tc-99m-3PRGD2 imaging before and 3 months after PB were reviewed. The tumor-to-occipital bone (T/O) and mirrored contralateral normal tissue-to-occipital bone (N/O) ratios were calculated by region of interest analysis at baseline and 3 months post-PB. T/O values were compared between patients with CM with comorbid secondary retinal detachment (RD) and those without RD. The relationship between T/O value and tumor volume was also investigated. Tc-99m-3PRGD2SPECT/CT showed focal uptake in CM. The mean T/O ratio before PB was 1.90 +/- 1.26 and the mean N/O ratio was 0.80 +/- 0.21 (P = .02). The Tc-99m-3PRGD2 concentrations in 5 patients with CM with RD were higher (T/O = 2.69 +/- 1.39) than in those without secondary RD (T/O = 1.10 +/- 0.18) (P = .008). T/O ratios at 3 months post-PB were significantly lower than that at baseline (1.23 +/- 0.59, P = .03). There was a linear relationship between T/O and tumor volume (y-hat = 0.028+ 0.003x, R-2 = 0.768, P = .001). The 95% confidence interval for the (T/O)/volume ratio was 0.002 to 0.005. Tc-99m-3PRGD2 imaging is a feasible modality for the diagnosis of CM. Furthermore, follow-up for at least 20 months after PB indicated that coanalysis of Tc-99m-3PRGD2 imaging and tumor volume may provide a promising prognostic predictor in patients with CM.