MainScene.cpp

//init  
  CCSize winSize = CCDirector::sharedDirector()->getWinSize();

   // Creating the CCParallaxNode
	_backgroundNode = CCParallaxNode::create();
	this->addChild(_backgroundNode, -1);

	_spacebg1 = CCSprite::create("mm-gfx/bg-mm.png");
	_spacebg2 = CCSprite::create("mm-gfx/bg-mm.png");

	CCPoint dustSpeed = ccp(0.1, 0.1);
	CCPoint bgSpeed = ccp(0.05, 0.05);

	_backgroundNode->addChild(_spacebg1, 0, dustSpeed, ccp(winSize.width / 2, winSize.height / 2));
	_backgroundNode->addChild(_spacebg2, 0, dustSpeed, ccp(_spacebg1->getContentSize().width, winSize.height / 2));
	
	this->scheduleUpdate();

//...
//update/tick function

void MainMenuLayer::update(float dt) {
	CCPoint backgroundScrollVert = ccp(-100, 0);
	_backgroundNode->setPosition(ccpAdd(_backgroundNode->getPosition(), ccpMult(backgroundScrollVert, dt)));
}

MainScene.h

#ifndef __MAINMENU_SCENE_H__
#define __MAINMENU_SCENE_H__

#include "cocos2d.h"

USING_NS_CC;

class MainMenuLayer : public cocos2d::CCLayer
{
private:
	CCParallaxNode *_backgroundNode;

	CCSprite* _spacebg1;
	CCSprite* _spacebg2;
	
	void update(float dt);
}