The effect of ignition promoters on H-2-O-2 detonation structure was evaluated with one-dimensional ZND calculations and experimental detonation cell measurements. Test conditions include a sweep of ozone concentration (up to 3000 PPM by mole), initial pressure (10 to 30 kPa), equivalence ratio (0.4-1.5), Ar and N-2 dilution (up to 50%), and CF3I concentration (up to 3000 PPM). The ZND calculations demonstrate that ozone addition reduces induction length without affecting heat release length or thermodynamic properties such as CJ speed, allowing for a unique evaluation of the effect of ignition delay on detonation structure. Experimentally and within the conditions tested, ozone addition acts to reduce detonation cell size by up to 70%. In addition, measured cell width is found to better correlate with induction length than with total reaction length, defined as induction length plus exothermic length. The results confirm that the detonation structure is controlled largely by chemical length scales. Also studied is the addition of CF3I, which is traditionally used as a fire suppressant. Although at high concentrations CF3I displays a radical scavenging function, at the concentrations considered in the current work, CF3I also acts as an ignition promotor due to the production of the I atom, which promotes chain branching during ignition. Finally, the ozone and CF3I additives were found to have, at most, a minor effect on cell regularity. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.