A practical approach for the determination of the quantum efficiency of persistent spectral hole burning (PSHB) is suggested. The quantum efficiency is found from the experimental kinetics of hole formation. The method takes into account all primary mechanisms of dispersion for the hole burning kinetics and can be applied to the characterization and the comparison of materials with different mechanisms of hole burning. The quantum efficiency of PSHB has been found for free-base and zinc naphthalocyanines, which have photochemical and photophysical mechanisms of PSHB, respectively. These materials are useful for PSHB applications in the spectral range around 800 nm.