We report a combined solid-state (1H, 2H, 13C, 17O) NMR and plane-wave DFT computational study of the O···H···O low-barrier hydrogen bonds (LBHBs) in two 1,3-diketone compounds: dibenzoylmethane (1) and curcumin (2). In the solid state, both 1 and 2 exist in the cis-keto-enol tautomeric form, each exhibiting an intramolecular LBHB with a short O···O distance (2.435 Å in 1 and 2.455 Å in 2). While numerous experimental (structural and spectroscopic) and computational studies have been reported for the enol isomers of 1,3-diketones, a unified picture about the proton location within a LBHB is still lacking. This work represents the first time that solid-state 17O NMR data are reported for the O···H···O LBHBs in 1,3-diketones. The central conclusion of this work is that detailed information about the probability density distribution of the proton (nuclear zero-point motion) across a LBHB can be obtained from a combination of solid-state NMR and plane-wave DFT computations (both NMR parameter calculations and ab initio MD simulations). We propose that the precise proton probability distribution across a LBHB should provide a common basis on which different and sometimes seemingly contradicting experimental results obtained from complementary techniques such as X-ray diffraction, neutron diffraction, and solid-state NMR can be reconciled.