Windows messages in child window

Question

I have a container window (CFrameWnd) that contains child windows, if I set the spy++ on a child window in some cases I do not see any message passing. Why? what 's the system that regulates messages between windows? I checked that all windows are enabled.

The child window inherits from CDialog and has the WS_CHILD style

class PanelDialog : public CDialog
{
    DECLARE_DYNAMIC(PanelDialog)

public:
    PanelDialog(CWnd* pParent = NULL);   // standard constructor
    virtual ~PanelDialog();

// Dialog Data
    enum { IDD = IDD_PANEL_DIALOG };

private:


protected:
    virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support

    DECLARE_MESSAGE_MAP()
};