With cocos2d 2.x, use the following :
CCLabelTTF *label = [CCLabelTTF labelWithString:inText
fontName:_defaultMenuItemFont
fontSize:_defaultMenuItemFontSize
dimensions:inSize
hAlignment:inAlignment
];
label.verticalAlignment = kCCVerticalTextAlignmentCenter;
i noticed that with one of the various 2.1 builds, you may have to do this AFTER setting the vertical alignment in order for it to work properly:
[label setString:inText];