<p>Emotion and motivation affect our perception, cognition, and action. Self-determined choice was previously applied in behavioral and neuroscientific studies to experimentally investigate effects of intrinsic motivation on task processing, but little is known about neural interactions between intrinsic motivation and affective processing. Here, we aim to investigate whether self-determined choice and affective picture content jointly or independently influence the late positive potential (LPP), associated with adjustments in attention allocation, during task processing. The presence of an interaction would indicate overlapping mechanisms. Additionally, effects of choice on task preparation were tested in the contingent negative variation (CNV). In two EEG experiments (<i>N</i> = 32 each), intrinsic motivation and affective picture content were manipulated under different cognitive task demands. In Experiment 1, a time production task, participants estimated two-second intervals while viewing affective pictures (neutral, negative, positive), with picture categories (e.g., humans, vehicles, animals) either self-chosen or assigned pseudorandomly (‘self’ vs.‘no choice’). LPP amplitudes were enhanced for negative compared to neutral and positive pictures and also in ‘self’ compared to ‘no choice’ trials. However, no interaction of self-determined choice and affective processing was found. Task preparatory CNV was not reliably different between choice conditions. Experiment 2 involved a less demanding active viewing task. The data replicate the evidence for independent LPP modulation by choice and affective picture content from Experiment 1 as well as the absence of choice-related CNV effects. The findings align with models on resource competition in attention allocation but suggest distinct processes for intrinsic motivation induced by self-determined choice and affective processing.</p>