Rotational coherence spectroscopy (RCS) has been applied to determine the rotational constants of the two isotopic species of the 9-cyanoanthracene (CNA)-water complex, CNA-H2O, and CNA-D2O. To support the experimental observation, DFT calculations at the B3LYP/6-31G(d,p) level have been also performed to identify several stable conformations. The structure of the complex is found to be such that water is hydrogen-bonded to the pi -electrons of the cyano group of CNA. Geometrical parameters consistent with the experimental results are evaluated.