The invention comprises radiolabeled oligonucleotide of the formula (I) wherein n, X1, X2, the linker 1, the linker 2, Q and the receptor targeting moiety are as defined I the description. The radiolabeled oligonucleotides of the formula (I) can be used for the determination of the biodistribution and pharmacokinetics of the oligonucleotide in the tissue or body fluid.