\documentclass[12pt]{article} \usepackage{comment} \excludecomment{conditional} \specialcomment{redcomment}{\em\Large}{\tiny} \begin{document} plain text. \newcommand{\Redcomment}[1]{Original Definition. (#1).} \begin{conditional} Conditional Text. More Conditional Text in next paragraph. \renewcommand{\Redcomment}[1]{Redefinition Worked! (#1).} \end{conditional} \begin{redcomment} the first redcomment paragraph. the second redcomment paragraph. \end{redcomment} Because redcomment has ended, this should be tiny. \Redcomment{This is the command line version.} \end{document}