Like so many issues here (and all through the green building world), this comes down to how you define green. Are you concerned primarily with the sourcing of the materials? With the energy consumed? With health issues? With durability? Or, more likely, a combination of these factors?
Reconstituted woods (sometimes also called engineered woods) are materials made of wood particles or fibers held together in some fashion, in contrast to solid wood or plywood. Particle board, a type of reconstituted wood, has gotten a bit of a bad rep due to weakness, vulnerability to moisture, and the contents of the most popular adhesives used to bind the particles.
Medium Density Fiberboard (MDF) is made from smaller particles, ironically making it stronger and more durable. For both -- as well as for most plywoods -- the binder frequently contains a carcinogen called urea formaldehyde. The green alternative is products made with binders using "no added formaldehyde." But you have to ask for them.
I was once told -- and I am guilty of repeating it without checking the fact -- that early reconstituted woods were made from scrap woods but that the demand outgrew the supply and now trees are cut to meet that demand. I'd love to hear from people who know whether this is true or not.
Green cabinets and green flooring
In terms of whether reconstituted wood is the best option for green cabinets and green flooring, though it is greener than many other materials, I can firmly answer: no, it is not the greenest. Better options might be salvaged wood or non-woods.
Salvaged wood has virtually no negative environmental impact. And I've used particleboard made from wheat stalks -- the waste material left over after the grain has been harvested. Unfortunately, it's become a bit harder to get and will probably cost more than the standard stuff.
So the basic answer to your question is a less-than-conclusive "maybe."
For more information:
You should also read Tracy Stone's Ask A Pro Q&A, "Where can I find unfinished wheatboard cabinets?"and Cynthia Phakos's Q&A "Can you recommend affordable green kitchen cabinets, flooring, and countertops?"