ABSTRACT: In this study we investigate tumor targeting T1 magnetic resonance imaging (MRI) contrast agents. The developed nanovector consists of ultrasmall Gadolinium Oxide (Gd2O3) Nanoparticles (GNPs) coated with TAT peptide. A simple one-pot synthesis of TAT peptide-conjugated ultrasmall GNPs to provide water solubility and to enhance biocompatibility. Paramagnetic properties of the TAT peptide-GNPs and their ability as contrast agents are demonstrated. The sample was characterized by HRTEM, XRD, FTIR spectroscopy and 1.5 tesla MRI Scanner techniques. The conjugate has a mean particle diameter 1.6 nm. The r1 value of TAT-GNPs was measured to be large r1=18.2 mM which is higher than that of commercially available Gd-DTPA (4.57 s-1 mM). The aqueous sample is not toxic for the tested concentration range, however, toxicity slightly increases with increasing concentration of Gd. The in vivo tumor targeting of the TAT-GNP was verified by obtaining T1 MR images of model mice with liver tumor after intervenous administration into the mouse tail. In the tumor region of the liver greater T1 contrast enhancement is observed than the normal part of the liver, owing to strongly accumulated TAT-GNPs into the tumor region.