Viroids are different from viruses in the following ways:\tIts RNA does not code for protein\tIt exists within the cells as RNA particles only with no envelope or capsid\tIt possesses only one circular RNA strand comprising of very few nucleotides\tContrary to viruses, viroids require no help of viruses to infect cells\tContrary to viruses of which the RNA can be copied in the nucleus or cytoplasm, the RNA of viroids are copied in the nucleus only\tTo detect the presence of viroids in the plant tissues, special techniques are used\xa0

Viroids are free RNA molecules of low molecular weight without any protein coat while viruses can have either RNA or DNA molecules encapsulated in a protein coat. Viroids are smaller in size than the viruses. Viroids infect only plants whereas virus infects all types of organisms. In viroids, protein coat is absent whereas in viruses a protein covering or a coat called as capsid is present around the genetic material.