(-)-9-Fluorocytisine, (-)-9-methylcytisine and (-)-9-trifluoromethylcytisine were synthesized from the natural product (-)-cytisine. 9-Methyl and 9-trifluoromethyl cytisines display a remarkable affinity at the alpha(4)beta(2) nicotinic receptor subtype (0.2 nM) with a high selectivity versus the alpha(7) nAChR subtype. Comparison of the affinity values suggests that the size of the substituent at the 9 position of (-)-cytisine seems more important than electronic factors for efficient binding and selectivity at alpha(4)beta(2) nAChRs. (C) 2010 Elsevier Ltd. All rights reserved.