Christian Dior Diorissimo was created by perfumer Edmond Roudnitska and released in 1956. According to Michael Edwards in Perfume Legends, Roudnitska was disturbed by the trend towards the heavier use of gourmand & sweet notes in perfumery, which resulted from efforts to balance out the new, sometimes harsh synthetics:
Not only were we pushing perfumes in the direction of food, but we were also putting too many ingredients into them. It made them too complicated and muddled. (quoted in Perfume Legends, p. 111)
Roudnitska was determined to simplify his approach; Diorissimo was the result. The fragrance notes are greens, bergamot, lily of the valley, ylang ylang, rosewood, amaryllis, boronia, jasmine, sandalwood, and civet.
The Eau de Toilette version of Diorissimo starts slightly sharp, with heavy green notes and a perfect lily of the valley accord. The lily of the valley continues to dominate, but there is also quite a bit of jasmine, and just a touch of wood. It is crisp and sparkling, very elegant, very young, and personifies spring like no other fragrance I know. It is not terribly long lasting, maybe a few hours at most.
The Parfum de Toilette is rather a different thing altogether. It is a deeper, sweeter floral, less sparkling, less green. The jasmine tends to take over the lily of the valley after an hour or so. It has a heavier animalic note, which might be from the civet, or perhaps from the indoles in the jasmine. It is a simply gorgeous fragrance, and the Eau de Toilette smells rather wan and pale in comparison.
All the same, I am not sure which version I prefer. I have been wearing Diorissimo for so long now that I am not sure I can really smell it properly, not in the sense of olfactory fatigue, for I don’t wear it that often, but simply because it is associated with so many old memories. The Eau de Toilette smells closer to what I remember wearing years ago, and while I suspect that it doesn’t smell quite the same as it used to, I adore it anyway.
The Parfum de Toilette version is unfortunately rather hard to find, so I have no advice on where to purchase it, and for that matter, I have no idea if Dior still produces a parfum version. The Eau de Toilette can be purchased at almost any of the online discounters.
Update 2/07: I have been wearing the parfum version of Diorissimo off and on over the past few months (so yes, it is still made!). Above, I called the Parfum de Toilette "simply gorgeous", and the parfum is even more gorgeous still. It is stunning. It is rich and deep, and Dior is clearly spending more money on the raw materials for the parfum than they are on the Eau de Toilette. It is a must-have, and luckily, can be found at decent discount prices if you shop around online; if you're willing to pay full price, it can be found at Saks. Still, it doesn't replace the Eau de Toilette. The Eau de Toilette remains the perfect thing when you need something crisp and sparkling and light on a summer day, and the Parfum, lovely as it is, isn't crisp and sparkling and light. So buy both.