The primary objective of this research study is to assess journalism students and journalists on their academic and disciplinary writing proficiency. The surveyed sample is composed of 104 participants, 52 journalism students from the Biobío region (Chile) and 52 professional journalists. The approach of the study is mixed and the analysis methodology applies a lexical availability model. The results show that the available lexicon of first and fifth year students is similar, revealing a poorly specialized lexicon. Journalism students view writing as a process of expression, communication, and transmission of ideas. In contrast, professional journalists have greater specialization than journalism students since they show use of sources and linguistic precision. It is concluded that the applied lexical availability model shows mental lexical changes in the sample surveyed and reveals the link between lexical availability and academic writing proficiency in journalism.