Most professional clarinets are made of a hard, black wood called Grenadilla. Beginner instruments are usually made of plastic, and plastic clarinets are also favoured in marching bands, because the sun and rain are not kind to wood. In the early 20th Century, many metal clarinets were made for the same reason, but most were of poor quality and they are no longer made.

There is an eternal debate as to whether the material of construction affects the sound or not. There is no doubt that cheap plastic instruments sound worse than expensive wooden ones, but the difference may be due to the care and attention lavished on the making of the wooden instruments. Plastic models are mass-produced to meet the educational market and therefore quality suffers. Scientific evidence seems to show that a well-made plastic clarinet will sound just as good as a wooden one, but this has not yet been accepted by the players, so manufacturers will continue to make the good clarinets from wood for some time to come.