although I'd say the substance is theine, we say decaffeinated for tea in Eng.

Clipper Teas

How is tea decaffeinated? Clipper uses a decaffeination process that uses no chemicals. ... The amount of caffeine in decaffeinated tea is less than 0.2%, ...
www.clipper-teas.com/is_faqs.htm
Teadirect Decaffeinated - a truly decent cup of tea. Take a moment to relax and enjoy a truly decent cup of Teadirect Decaffeinated in the knowledge that ...
www.cafedirect.co.uk/products/teadecaf.php
Tetley Naturally Decaffeinated - Review - Tealicious
Still I thought I’d try Tetley’s Decaffeinated Tea. So I managed to remember next time ... It wasn’t until the 1980s that decaffeinated tea was first made. ...
www.dooyoo.co.uk/drinks/tetley-naturally-decaffeinated/1000...

--------------------------------------------------
Note added at 17 mins (2006-01-26 11:36:37 GMT)
--------------------------------------------------

a little more info. (+ more available via the link...)


4. Is it true that tea has no caffeine/What is theine, theobromine, etc?

From "Principles of biochemistry", Horton and al, 1993.

Caffeine is sometimes called "theine" when it's in tea. This
is probably due to an ancient misconception that the active
constituent is different. Theophylline is present only in
trace amounts. It is more diuretic, more toxic and less
speedy.

Caffeine
1,3,7-trimethylxanthine
Theophylline
1,3-dimethylxanthine
Theobromine
3,7-dimethylxanthine

Coffee and tea contain caffeine and theophylline,
respectively, which are methylated purine derivatives that
inhibit cAMP phosphodiesterase. In the presence of these
inhibitors, the effects of cAMP, and thus the stimulatory
effects of the hormones that lead to its production, are
prolonged and intensified.

Theobromine and theophylline are two dimethylxanthines that have two
rather than three methyl groups. Theobromine is considerably weaker
than caffeine and theophylline, having about one tenth the stimulating
effect of either.

Theobromine is found in cocoa products, tea (only in very small
amounts) and kola nuts, but is not found in coffee. In cocoa, its
concentration is generally about 7 times as great as caffeine.
Although, caffeine is relatively scarce in cocoa, its mainly because
of theobromine that cocoa is "stimulating".

Theophylline is found in very small amounts in tea, but has a stronger
effect on the heart and breathing than caffeine. For this reason it is
often the drug of choice in home remedies for treating asthma
bronchitis and emphysema. The theophylline found in medicine is made
from extracts from coffee or tea.

http://nootropics.com/caffeine/faq.html