This paper investigates whether changes in mood state are an important component of cognitive bias modification (CBM) procedures. In a novel CBM procedure participants read either positive or negative statements relating to social issues for 5 min. Interpretation bias was measured by means of a scrambled sentence test, which was presented both before and after the CBM procedure. Participants who read the positive statements made more positive resolutions to the scrambled sentences, while participants who read the negative statements made more negative resolutions. Thus, the appropriate positive and negative interpretative biases were induced by the CBM procedure. However, significant mood changes also occurred following CBM. In Experiment 2, a musical mood induction procedure was presented with depressing or elating music. As before, a scrambled sentence test was presented both before and after the musical mood induction. Mood changed in accordance with the valence of the music to the same extent as with CBM. Critically however, performance on the scrambled sentence task did not change for both groups. This demonstrates that a change in mood state is not sufficient for a change in cognitive bias to occur.