Development of new digital means requires teachers to dispose such level of didactic technological competences to be prepared properly to implement them into their teaching practice and to be not afraid to use them within their lessons. These facts evoke a need continuously to innovate curricula of the relevant part of teacher trainee study programs, to acquaint future teachers with the newest kinds and versions of available didactic tools and with advantages of their use to support both teaching and learning processes. A question how to design an optimal model of teacher training in the area of teacher trainees' didactic technological competences evoked a need to assess strengths and weaknesses of in-service teachers as to their professional digital literacy The paper presents a case study the aim of which was to assess level of the digital literacy of primary and secondary school teachers in Slovakia based on their self-reflection. Research sample of the case study consisted of 173 teachers, participants of teacher continuous education, representing three of eight regions of Slovakia. The teachers were asked to assess level of their digital literacy in relation to 17 of selected software applications used in teaching practice, i.e. to assess how skilled they are to use these means in their own teaching practice. Analysis of the teacher self-reflection was done in dependence on their majors (subjects they are qualified to teach) and teaching staff category they belong to. Results of statistical analysis of the collected data pointed out some important facts that should be reflected in innovations of the relevant area of curricula of teacher study programs at universities, or also in programs of further education of in-service teachers. However, data collection to the presented research was carried out before the corona pandemics. Nowadays, when under the corona pandemics conditions education is moving into the virtual reality and dominantly using on-line forms we see that even more important than to train teachers to use digital technologies in general is to train them to work with different application systems used in on-line education processes.