Background:　This　attractive　and　intriguing　Ribonucleic　acid　(RNA)　nanotechnology　has　been　conceptualized　over　the　last　two　decades　and　with　our　increasing　understanding　of　RNA　structure　and　function　and　improvements　of　RNA　nanotechnology　it　is　now　possible　to　use　this　in　clinical　settings.　Methods:　Here　we　review　the　unique　properties　and　the　recent　advances　in　RNA　nanotechnology　and　then　look　at　its　scientific　and　preclinical　applications　for　tumor　diagnosis　and　targeted　delivery　and　RNA-based　therapy　using　RNA　nanoparticles　with　diverse　structures　and　functions.　Finally,　we　discuss　the　future　perspectives　and　challenges　to　RNA　nanotechnology.　Results:　RNA　can　be　designed　and　manipulated　in　a　similar　way　to　DNA　while　having　different　rules　for　base-pairing　and　displaying　functions　similar　to　proteins.　Rationally　designed　RNA　nanoparticles　based　on　the　three-way　junction　(3WJ)　motif　as　the　core　scaffold　have　been　extensively　explored　in　the　field　of　nanomedicine　and　targeted　cancer　diagnosis　and　therapy.　Conclusions:　RNA　nanostructures　based　on　3WJs　demonstrate　promising　future　applications　due　to　their　thermal　stability,　molecular-level　plasticity,　multifunctional　chemotherapeutic　drug　delivery　and　other　intrinsic　characteristics,　which　will　greatly　improve　the　treatment　of　cancer　and　promote　further　major　breakthroughs　in　this　field.