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Abstract The T₁of a hyperpolarized site in solution is a key parameter that determines the time‐window in which its NMR signals are observable. For¹³C sites adjacent to protons,¹H‐decoupling has been shown to increase the hyperpolarized signal resolution and SNR. Additionally, polarization transfer to protons has shown utility in increasing the sensitivity of detection. However,¹H‐decoupling could lead to a change in the decay rate of a hyperpolarized¹³C site. Here we tested this possible effect in a case where the protons are directly bound to an sp³hyperpolarized¹³C site (using [1,2‐¹³C₂]choline) and¹H‐decoupling was applied continuously throughout the hyperpolarized decay measurement. We found that¹H‐decoupling did not lead to any significant changes in the¹³C polarization decay time but did result in the expected collapse of J‐coupling and produced sharper signals. This result suggested that¹H‐decoupling did not affect the decay rate of hyperpolarized sp^{3 13}C sites. The deuterium‐substitution approach (using [1,1,2,2‐D₄,1‐¹³C]choline) showed a dramatic prolongation of T₁. Upper bounds on the T₁of all investigated sites were calculated.