Structural and energetic features of the complex 1,4-difluorobenzene-ammonia have been investigate by rotational spectroscopy. The complex adopts a sigma configuration, with the nitrogen of ammonia in the plane of the aromatic ring. Two weak hydrogen bonds, C-H center dot center dot center dot N and N-H center dot center dot center dot F, represent the linkages between ammonia and 1,4-difluorobenzene. (C) 2009 Elsevier B. V. All rights reserved.