The selective protection of D-Phe1-octreotide peptide (I) with Boc2O gives the monoprotected peptide (II), which is condensed with diethylenetriaminopentaacetic acid (DTPA) dianhydride (III) by means of NaHCO3 in dioxane/water to yield the adduct (IV). The treatment of (IV) with TFA affords the desired DTPA-octreotide derivative (V), which is finally labeled with 111InCl3 in acetic acid or in ammonium citrate to afford the target indium derivative. The starting D-Phe1-octreotide peptide (I) has been obtained by the conventional methods of peptide synthesis using a peptide synthesizer.