In the begining of my document, I've used \frontmatter in order to switch page numbering to Roman numerals and \mainmatter to end this up and returning to Arabic numerals.
Why the page numbers of all 'addcontentsline{toc} {chapter} {my_CONTENT}' between the block \frontmatter\mainmatter aren't shown in table of contents?
• Welcome to TeX.SX! Please help us help you and add a minimal working example (MWE) that illustrates your problem. Reproducing the problem and finding out what the issue is will be much easier when we see compilable code, starting with \documentclass{...} and ending with \end{document}. – dexteritas Feb 7 at 7:55