This review focuses on the use of functionalized carbon nanotubes (CNTs) on the development of preconcentration methods with substantial contributions on selectivity and sensitivity for metal ions determination. CNTs have been usually employed in the development of preconcentration/speciation coupled to spectroanalytical techniques for ions determination at trace levels in different kind of samples. With regard the electroanalytical ones, this material has been widely used in adsorptive voltammetry procedures. Despite intrinsic features of CNTs, they suffer from poor dispersion in aqueous medium and wettability, thus making them very useful for sorption of hydrophobic metallic complex, but few indicated for metallic ions. Thus, different syntheses strategies, purification and chemical and physical approaches for surface functionalization/modification have been reported for improving the applicability of CNTs for a wide range of analytes. Therefore, apart from the brief description of the main physical and chemical characteristics of the carbon nanotubes, this review report the critical evaluation of main applications of modified CNTs as solid phase and as electrodic material for metal ions determination in environmental samples, food and biological using spectroanalytical techniques such as flame and graphite furnace atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry and electroanalytical mainly the adsorptive voltammetric ones.