Beyond the biological consequences, photo-generation of electron holes in G-quadruplexes may inspire applications in nano-electronics; although four-stranded structures are currently studied as molecular wires, their behavior as photoconductors has not been explored so far.In the present Account, after highlighting some key experimental issues, we first describe the photo-ionization process and, then, we focus on radicals. We use as show-cases new results obtained for genomic DNA and Oxytricha G-quadruplexes. Generation and reaction dynamics of G radicals in these systems provide a representative picture of the phenomena reported previously for duplexes and G-quadruplexes, respectively.