Compiled from the Note Identification Project thread:
Hydroxycitronella – Muguet! there is definitely a lot of this stuff in Diorissimo.
Hydroxycitronella – Mild, tiny white flower, lily-of-the-valley. Very well-mannered. Needs support, but nice.
Hydroxycitronellal: soft and delicate lily of the valley, but somewhat flat. To my nose, it lacks a "bright" side. My immediate impression was that I smell this note, or a similar one, in 90% of floral perfumes. This is the classic LotV note, the synth Roudnitska used in Diorissimo.
Hydroxycitranella: very sweet, slightly anise-y I think - small resemblance to Lolita Lempicka Au Masculin. Perhaps with a tiiiiiny bit of orange/citrus.