At my clinic we do shihtzu and lhasa rescue, i guess a couple ways to tell would be 1. underbite, all shihtzus have it 2. shihtzus have eyes that pop out of their heads, theyre not in the eye socket like a lhasas would be 3. shihtzus are stalkier, lhasas are usually thinner, mostly you can tell the difference in the face, shitzus will have an underbite, bigger, bulging eyes, and a very short snout, while lhasas will have a longer snout, and normal eyes. Hope this helps.