I have main fsm with two sub-levels. The problem is, the sub-fsms need data which is held in root fsm, like: struct SomeAction { template <typename EVT, typename FSM, typename SourceState, typename TargetState> void operator()(EVT&, FSM& fsm, SourceState&, TargetState&) const { // ... } }; Instance of fsm here might be root fsm as well as sub-fsm. I see two possible solutions: 1. use sm_ptr policy and store parent pointer in each sub-fsm In this case access might look like this: fsm.parent_->data; (access from 1-level fsm) fsm.parent_->parent_->data; (access from 2-level fsm) doesn't look so nice, besides, documentation states that using sm_ptr is deprecated. 2. recursively traverse all states, detect fsm's and store root pointer typedef RootFSM::stt stt; typedef boost::msm::back::generate_state_set<stt>::type all_states; boost::mpl::for_each<all_states, boost::msm::wrap<mpl::placeholders::_1> > (find_sub_fsm<stt>()); template <typename stt> struct find_sub_fsm { template <class StateType> void operator()(boost::msm::wrap<StateType>& state) const { // ??? // state.root_ = &g_root; // do the recurs } }; How to detect that StateType is sub-fsm? 3. Maybe, there is a easier way to communicate between sub-fsm's?