Intrigued by the positive effect in terms of potency displayed by cyanine dye conjugation and of selectivity showed by folate labelling, we sought to combine both strategies and generate dual labelled constructs 13-15, where the α-amine of the N-terminal lysine is conjugated to cyanine dye 1 and the side chain of the same lysine is conjugated to the folate. Notwithstanding the enhanced potency compared to the parent sequences and to compounds 10-12, dual labelled constructs did not display the expected selectivity towards KB cells. The observed lack of selectivity may be due to a failed interaction between the folate component and the folate receptor α because of the presence of the cyanine dye on the same residue. In fact, the steric environment around the folate fragment is known to be an important factor for the interaction of the conjugate with the receptor. Therefore, future work will vary folate and cyanine dye position in the construct to obtain dual labelled compounds with the best cytotoxicity and selectivity.