Socially desirable responses have been widely discussed as potentially biasing self-reported measures of environmental attitude and behaviour assessment. The direct and moderating effect of social desirability on children has not been analysed before. By applying a Lie scale together with a two-factor environmental attitude set measure and a scale of self-reported General Ecological Behaviour (GEB) to 198 pupils, we found a moderate impact of Lie scores on only one of both attitude measures and a small impact on GEB. In a multiple regression analysis general behaviour was predicted by attitude, social desirability, and the interaction of both. Social desirability had no moderating effect on the relationship between environmental attitudes and behaviour. Implications of these outcomes for research on environmental issues with children are discussed. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Socially desirable responses have been widely discussed as potentially biasing self-reported measures of environmental attitude and behaviour assessment. The direct and moderating effect of social desirability on children has not been analysed before. By applying a Lie scale together with a two-factor environmental attitude set measure and a scale of self-reported General Ecological Behaviour (GEB) to 198 pupils, we found a moderate impact of Lie scores on only one of both attitude measures and a small impact on GEB. In a multiple regression analysis general behaviour was predicted by attitude, social desirability, and the interaction of both. Social desirability had no moderating effect on the relationship between environmental attitudes and behaviour. Implications of these outcomes for research on environmental issues with children are discussed.