Comparison of the affinity towards adenosine receptors of 2-phenyl-8-azaadenosines, bearing a lipophilic substituent on N(6), with the corresponding 2-phenyl-8-azaadenines was carried out. The compounds have good A(1) affinity and high A(1) selectivity. The obtained Ki(rib)/Ki(benz) ratios for A(1) receptors, which showed variable values depending on the structure of the N(6) Substituent,confirmed that 2-phenyl-8-azaadenines are characterized by greater freedom inside A(1) receptors. This situation may be a favourable test of the hypothesized double disposition of these exogenous molecules within A(1) receptors.