A series of 1,4-substituted arylalkyl piperazine derivatives were synthesized and studied with the aim to obtain potent P-gp-dependent multidrug-resistant (MDR) reversers. The new compounds were designed on the basis of the structures of our previous arylamine ester derivatives endowed with high P-gp-dependent multidrug resistance reversing activity. All new compounds were active in the pirarubicin uptake assay on the doxorubicin-resistant erythroleukemia K562 cells (K562/DOX). In particular, compounds bearing methoxy aromatic moieties showed fairly high reversal activities. The most potent compounds, 8, 9, 10 and 13, were further studied by evaluating their doxorubicin cytotoxicity enhancement (reversal fold, RF) and the inhibition of P-gp-mediated rhodamine-123 (Rhd 123) efflux on the K562/DOX cell line. The results of all pharmacological assays indicated that the combination of a basic piperazine scaffold with arylalkyl residues allowed us to obtain very interesting P-gp modulating compounds. Two long-lasting P-gp pump modulators (9 and 10) were identified; they were able to inhibit remarkably the P-gp substrate rhodamine-123 efflux on the resistant K562/DOX cell line after 60 min. Overall compound 9 appeared the most promising compound being a potent and long-lasting P-gp-dependent MDR modulator.