Application of (13)C MRS in vivo on whole body MR system has been limited due to the low static field (and consequent low signal to noise ratio-SNR) of these scanners; thus there have been few reports of (1)H decoupled (13)C MRS in vivo using a clinical MR platform. The recent development of techniques to retain highly polarized spins in solution following DNP in a solid matrix has provided a mechanism to use endogenous pre-polarized (13)C labeled substrates to study real time cellular metabolism in vivo with high SNR. In a recent in vivo hyperpolarized metabolic imaging study using (13)C pyruvate, it has been demonstrated that the line shape (signal decay) of the resonances observed are greatly affected by J(CH) coupling in addition to inhomogeneous broadening. This study demonstrates the feasibility of improving hyperpolarized (13)C metabolic imaging in vivo by incorporating (1)H decoupling on a clinical whole body 3T MR scanner. No reduction of T1 of a pre-polarized (13)C substrate ([1-(13)C] lactate) in solution was observed when (1)H decoupling was applied with WALTZ16 sequence. Narrower linewidth for the [1-(13)C] lactate resonance was observed in hyperpolarized (13)C MRSI data in vivo with (1)H decoupling.