Lanthanide-catalyzed addition of diethyl phosphite with chalcones was achieved under mild conditions. The reaction exhibited good product selectivity using different catalysts. γ -Oxophosphonates were obtained in high yields in the reactions catalyzed by Yb(OAr) 3 (THF) 2 , while those catalyzed by [(Me 3 Si) 2 N] 3 La(μ-Cl)Li(THF) 3 afforded 1,2-oxaphospholane-5-phosphonates as the main products in moderate to good yields. This methodology provides facile and practical approaches to the corresponding organophosphorus compounds with biological interest. C 2013 Wiley Periodicals, Inc. Heteroatom Chem. 24:345-354, 2013; View this article online at wileyonlinelibrary.com.