Radio, a mass medium for transmitting signal using electromagnetic waves, was created in 1913. From its beginnings, it has proven to be a real vehicle for disseminating information by virtue of being convenient to listen to at any place, at any time. The role of radio was different in times of war and after. This final paper presents the role of radio inthe era of the Kingdom of Serbs, Croats and Slovenes and laterinthe time of the NDH, during the crisis that hit Croatia inthe 20th century. Legal regulations were introduced to restrict the freedom of speech of journalists, and there were bans on the transfer of state secrets. Those who would not comply with the law would be sanctioned. Sanctions could have been for feiture of the apparatus, up to the death penalty. In 1924, the first radio amateur club was opened in Zagreb, and in 1926, a radio broad cast began. Dr. Stern was the first director of a radio station and believed that he worked exclusively in the medium of culture and education. The crisis period slightly disrupted radio activity because only short news, alarms, and political status in the country were broadcast during the war. There were also secret radio stations that were false lyposing as friendly organizations aimed at attacking the Croatian territory, with many radio stations in a lull. After the situation in the country calmed down a little, a total of 50 Croatian radio stations were active. However, the barrier was now the advent of television. The aim was to look to national broadcasters to increase the role of radio, which was successfully done. Important personalities who were responsible for the successful development of radio will remain mentioned, as well as the most important programs and shows. The aim of the final paper was to present the role of radio in Croatia inthe 20th century, which led to the conclusion that radio played an important role in every period in history. During the crisis, radio was the mainmeans of alarming the bombing, while after the war it was given the role of a media with fun, educational, cultural content.