Psychological Operations (PSYOPS) and Military Deception (MILDEC) constitute a particularly important element of information warfare and of influencing the perception, as well as the decision- -making process, of the opponent. The aim of this article is to systematise knowledge of the methods, techniques and tools used to conduct modern PSYOPS and MILDEC and to identify the main similarities and differences between them. The research problem posed in the conducted research was formulated in the form of the following question: how are PSYOPS and MILDEC conducted? The following research hypothesis was formulated for the research problem posed in this way: PSYOPS and MILDEC, although aimed at influencing the cognitive sphere of the opponent and influencing the way he makes decisions, and the similarities between them, use different ways of achieving the goals assumed by the conductor of specific actions, and direct conversations, mass media, including Internet portals, are used to conduct them. At the same time, the nature of the content produced by PSYOPS and MILDEC is also different. The question was answered and the hypothesis was verified using the following theoretical research methods: literature analysis and criticism, definition, synthesis and comparison. Doctrinal documents, monographs and compact studies, as well as academic articles and internet sources were used for the literature analysis. A limitation in access and selection was the choice of only non-classified documents. The paper characterises PSYOPS and MILDEC, then compares and, on the basis of these, demonstrates commonalities and differences in their planning, in the ways and tools used to conduct them, as well as the main challenges to increasing their effectiveness and minimising their potential negative effects.