Psoriasis represents a common, chronic inflammatory disease involving the skin, nails and joints. Nail psoriasis in usually investigated and diagnosed by clinical examination. New insights support ultrasonography as being a non-invasive reliable imaging technique for studying nail and skin involvement in patients with psoriasis. Power Doppler frequency, higher than 10MHz enables a very sensitive detection and semiquantitative assessment of the blood flow at the dermal level and in the nail bed. In this review we will present the main US findings in skin and nail psoriasis, and discuss the importance of ultrasonography in diagnosing and monitoring psoriasis vulgaris.