CNTs are a new type of nanomaterial that is attracting attention as gene therapy vectors due to their unique advantages such as large aspect ratio, good biocompatibility, superior mechanical properties, and ease of functionalization. Despite their promising advantages, the use of primitive CNTs in biomedical applications has been limited by their highly hydrophobic surface, which results in poor water solubility and dispersion. Recent studies have shown that CNTs can be surface modified or functionalized using a variety of physicochemical means, making them a new and ideal gene transfer vector. CNTs can be used as excellent carriers for plasmid DNA, small interfering RNA (siRNA), and microRNA with different types of functionalized modifications (e.g. polycations).