The similarities are...
- they both have DNA chromosomes (although prokaryotes have DNA chromosomes in the form of a single stranded loop and eukaryotes have DNA chromosomes that are linear and thread like)
- they both have ribosomes (although ribosomes in prokaryotes are scattered in the cytoplasm and ribosomes in eukaryotes are either attached to the rough ER or free in the cytoplasm)
- they both have cell membranes
- some prokaryotes (bacteria) and some eukaryotes (fungi, plants and some protists) have cell walls