Driven by the documented effectiveness of cryoradiolysis coupled with resonance Raman spectroscopy for the preparation and structural characterization of unstable peroxo and hydroperoxo intermediates of catalytic and oxidative enzymes, similar strategies have now been applied to prepare and study the still relatively unexplored chemistry of nitrosyl hydride (HNO) adducts of heme proteins and their derivatives. Previously, such HNO derivatives of heme proteins were prepared by chemical addition of reducing agents or by direct addition of an HNO donor. Here, for the first time, we report effective cryoradiolytic preparation of Fe–N(H)O species of myoglobin and their structural characterization by resonance Raman spectroscopy. Our results are in excellent agreement with those previously reported for chemically prepared derivatives and with computational results. Furthermore, the present study provides new data for the deuterated analogue; i.e. bearing a nitrosyl deuteride (DNO) fragment. Copyright © 2012 John Wiley & Sons, Ltd.