There are a total of 22 3-letter words containing 'oo', and the number may vary in different dictionaries. You can specify the dictionary and order.

• boo ₆
• coo ₆
• foo ₆
• goo ₅
• loo ₄
• moo ₆
• noo ₄
• oof ₆
• ooh ₅
• oom ₆
• oos ₃
• oot ₃
• poo ₆
• roo ₃
• too ₃
• woo ₆
• zoo ₁₂
• hoo ₆
• doo ₄
• oon ₃
• oop ₅
• oor ₃

There are 22 3-letter words containing "oo" in the well-known word game dictionary, 16 in the Scrabble US (US/Canada/Thailand - TWL/NWL) dictionary, and 21 in the Scrabble UK (International - SOWPODS/CSW) dictionary, and 17 in the Words with Friends (WWF) dictionary.