Both Psoriasis and eczema can show similarity in having a rash, presenting with itching over the skin and can involve similar body parts such as hands and legs.
The major difference between the two is that psoriasis is commonly seen on the backside of the elbows and front of the knees whereas eczema is commonly presented over the inner aspect of the elbows and knees i.e. the cubital fossa and the popliteal fossa respectively.