A series of N-(benzofuran-2-ylmethyl)-N'-benzylpiperazines bearing alkyl or fluoroalkyl aryl ethers were synthesized and evaluated at various central nervous system receptors. Examination of in vitro sigma1 {[3H]+-pentazocine} and sigma2 ([3H]DTG) receptor binding profiles of piperazines 11-13 and 25-36 revealed several highly potent and sigma1 selective ligands, notably, N-(benzofuran-2-ylmethyl)-N'-(4'-methoxybenzyl)piperazine (13, Ki=2.7 nM, sigma2/sigma1=38) and N-(benzofuran-2-ylmethyl)-N'-(4'-(2''-fluoroethoxy)benzyl)piperazine (30, Ki=2.6 nM, sigma2/sigma1=187). Structural features for optimal sigma1 receptor affinity and selectivity over the sigma2 receptor were identified. On the basis of its favorable log D value, 13 was selected as a candidate for the development of a sigma1 receptor positron emission tomography radiotracer. [11C]13 showed high uptake in the brain and other sigma receptor-rich organs of a Papio hamadryas baboon. The in vivo evaluation of [11C]13 indicates that this radiotracer is a suitable candidate for imaging the sigma1 receptor in neurodegenerative processes.