This study analyses the thematic and conceptual structure of the Spanish scientific production published in Emerging Sources Citation Index (Web of Science) journals. In this way, the aim is to identify the closest links between concepts and terms based on the co-occurrence of keywords used by the authors of the papers analysed, and also to point out the theoretical foundations that exist in the discipline through the co-citation relationships of articles in the bibliography of the documents in the sample. Finally, these results were compared with those obtained from the analysis of Spanish scientific production in Social Sciences Citation Index (SSCI). To achieve these objectives, a network analysis of the co-occurrence of keywords and co-citation of references in articles published in Communication journals between 2015 and 2021 in ESCI (N = 3,559) and SSCI (N = 1,738) with at least one author linked to a Spanish institution was carried out. The results point to similar structural cohesion values and to a thematic and methodological similarity between both sets observed. There is a marked tendency towards quantitative studies on new technologies. While in SSCI there is an almost absolute dominance of Journalism studies, in ESCI there is a greater diversity of other disciplines such as Audiovisual Communication or Advertising. However, the intellectual structure of the production in SSCI reflects a more specialised character than in ESCI. [ABSTRACT FROM AUTHOR]