Poly[ethylene-co-(butyl acrylate)-co-(carbon monoxide)] (polyEBC) samples, prepared from 13C-labeled carbon monoxide, were characterized using two dimensional (2D) pulsed field gradient (PFG) 750 MHz NMR spectroscopy. To elucidate the complex mixture of structures present in this terpolymer, 2D 1H/13C-heteronuclear multiple bond correlation (HMBC) experiments were conducted by selectively exciting the enhanced peaks resulting from 13C-labeling. High resolution 2D NMR combined with 13C-labeling of the polymer greatly simplifies the 2D NMR spectra, selectively enhances the weak peaks from low occurrence C-centered triad structures and aids in their resonance assignments.