I wanna mount an entity on the players head. How can i make that it isn't displayed 2 blocks above his head?

MC Version?

 

Mounting entity has offsets:

public void updateRiderPosition()
    {
        if (this.riddenByEntity != null)
        {
            this.riddenByEntity.setPosition(this.posX, this.posY + this.getMountedYOffset() + this.riddenByEntity.getYOffset(), this.posZ);
        }
    }

    public double getYOffset()
    {
        return 0.0D;
    }

    public double getMountedYOffset()
    {
        return (double)this.height * 0.75D;
    }

 

Your entity mounting player has probably bad height and/or offsets.