Probably these three bred cats had some common ancestors. Then, the different climates where all those cats moved, have changed some details :

If we start from the general appearance of those three cats, we can notice that these three cats are big, strong and their look is just power and sweetness.
The biggest is certainly the Maine coon cat.
The Maine coon and the Norwegian forest cat are large cats and have high paws, whereas the Siberian cat is a semi-cobby which the body and the general appearance look like a little barrel.

Panthera del Andalucia - Maine coon Nirvana Bagheera's cattery

Olav du Bois d'Opio - Norwegian Artannes'cattery

Comrade Aleksey Pasanovich - Siberian St Thomas'cattery (Canada)

We also find differences on the head of these 3 cats : The Norwegian forest cat's head is triangular. Its profile is straight and its eyes are sidelong glance with an almond shape.
The Maine coon has a square head, its profile is marked by a nose stop and its eyes are rounded.
The Siberian cat has a rounded head. Its profile is characterized by a small curve above the nose and its eyes are oval.
At last, we can say the Maine coon and the Norwegian forest cat' ears are large whereas the Siberian cat has medium size ears and rounded.

Panthera del Andalucia - Maine coon Nirvana Bagheera's cattery

N-Ynglesildra's Joril - Norwegian Osmondes'cattery

Iz Ermitage Irinam - Siberian Artannes'cattery

Find in "El mundo del gato", june 2000.

We have to make a difference between the Neva masquerade (or colorpoint Siberian cat), the Birmans and sometimes the Ragdoll. They just have in common the colorpoint pattern of their coat and their semi-long haired coat. That's all. If each cat is a nice representative of its breed, we can't mix them up.