[Wil"]

why Carbon dioxide, carbon monoxide are not considered as organic substance, even they both contain carbon?

[Borek]

why Carbon dioxide, carbon monoxide are not considered as organic substance, even they both contain carbon?

By definition.

[Albert]

http://en.wikipedia.org/wiki/Organic_chemistry

Check out the first paragraph.

[HP]

"Why not?" is the question no true chemist can answer you with pure mind and heart  If there's no reason these compounds not acepted as true organic molecules, by my opinion some burocratic person(s) has decided this pure absurd to be writen as  paragraph in existing chemistry paradigmas...Arguing against  paradigmas, every reason man can concider these 2 compounds as truly organic - so "organic" that CO2 is what plants are consuming for next all animals to can feed with, and CO is one of the most important reagents in the primitive Earth atmosphere for later life to be born from, and also a key compound in Industrial organic synthesis (see hydroformilation reactions, Reppe process and many others)
P.S. As i know HCN and its isomer HNC: are acepted as organic molecules and also their molecule weights are 1 less than that of CO and the second isomer is structurally very similar to C=O polarized form (see parahors of CO and isocyanides)...

[pantone159]

I'm inclined to call them organic, but I'm not really a chemist so I don't care if that is officially 'right' or not.
I'd also count diamond, and graphite (which has C-C pi bonds, after all) as 'organic'.  It's just a technicality, though.

[HP]

I can (some eretically concider the "all-carbon" molecules like graphite, diamond, fullerenes and C-nanotubes as organic molecules and many of their H,O,N etc. derivatives. If someone say : "C60 is not organic mol" then i'll ask him "then what about C60-OH?" .
Also do you accept the free :CH2  molecules (as singlet or tr methylene) as organic molecules of C(II) kind which polymerize to polyethylene and by the way CO copolymerize with CH2O for example to all organic polymer too Well if someone has studied organic chemistry without passion of for example "synthesis aspirin from coals" then other fellow may say: i'll study chemistry of carbon itself and of it's compounds