  Comparison of properties of quark and leptons as well as understanding their
similarities and differences is one of the milestones on the way to underlying
physics. Several observations, if not accidental, can strongly affect the
implications: (i) nearly tri-bimaximal character of lepton mixing, (ii) special
neutrino symmetries, (iii) the QLC-relations. We consider possible connections
between quarks and leptons which include the quark-lepton symmetry and
unification, approximate universality, and quark-lepton complementarity.
Presence of new neutrino states and their mixing with the left or/and right
handed neutrinos can be the origin of additional differences of quarks and
leptons.
