Aptamers, including DNA, RNA and peptide aptamers, are a group of promising 
recognition units that can specifically bind to target molecules and cells. Due 
to their excellent specificity and high affinity to targets, aptamers have 
attracted great attention in various fields in which selective recognition units 
are required. They have been used in biosensing, drug delivery, disease 
diagnosis and therapy (especially for cancer treatment). In this review, we 
summarized recent applications of DNA and RNA aptamers in cancer theranostics. 
The specific binding ability of aptamers to cancer-related markers and cancer 
cells ensured their high performance for early diagnosis of cancer. Meanwhile, 
the efficient targeting ability of aptamers to cancer cells and tissues provided 
a promising way to deliver imaging agents and drugs for cancer imaging and 
therapy. Furthermore, with the development of nanoscience and nanotechnology, 
the conjugation of aptamers with functional nanomaterials paved an exciting way 
for the fabrication of theranostic agents for different types of cancers, which 
might be a powerful tool for cancer treatment.