French, like most Romance languages, displays both prenominal and postnominal placement of at-tributive adjectives. The fact that choice in position is not random led many linguists (Abeille and Godard (1999); Forsgren (1978); Wilmet (1981)) to propose constraints based on different dimensions of language (syntax, semantics, phonology, morphology, pragmatics...), but most of them are only trends and it is very difficult to draw a general picture of the phenomenon. We thus proposed in a previous work (Anonymous (tted)) a prediction model built on data from the French Treebank corpus (FTB) (Abeille et al. (2003)), along the lines of Bresnan et al. (2007), based on most of the proposed constraints, to test the contribution weight of each of them and the impact of their interaction. Even if results were encouraging, several facts were outlined: first, if introspection leads to the conclusion that most adjectives alternate, usage shows much more fixity: less than 10% of the adjectives in our data are actually in both positions. This suggests that locutors' mental representations for every item are in fact much stronger for a given position compared to its counterpart. Second, some contrainsts dont have a significant effect in our model. Yet, a qualitative exam showed that they are greatly correlated to a position for specific adjectives. For instance, different 'different', which appears equally in both positions, displays for each position a pattern linked to the nature of the determiner, whereas the type of determiner is not relevant at a more general level. More precisely, we observe a strong cooccurrence of a definite determiner with different in anteposition and a similar pattern between the indefinite determiner and the postposed adjective. This indicates that some constraints are relevant, but only for specific adjectives. Like (Bybee and Mcclelland (2005); Goldberg (2006); Croft (2001)) we believe that locutors' knowledge is based on much more specific information on the item, but also on the context in which it appears: formal characteristics of a particular sequence, frequency of use, distributionality... This work focuses on a qualitative study, on another corpus (ER (2010) 147,934,722 tokens), of the adjectives identified as displaying this alternation in the FTB, the aim being to better understand their functioning, and to propose a model that will better handle actual usage in the FTB. Our methodology is inspired by Gries and Stefanowitsch (2004): we search which lexical elements occur in a particular pattern and identify their attraction strength to the construction by means of a statistical analysis. Results show different types of behaviour on a continuum going from very fixed general patterns to more alternation. The first class of adjectives is very close to the fixed position adjectives: they massively prefer a given position, except in a few cases of idiomatic/collocational sequences. For instance, majeur 'major' is always postposed to the noun, unless it is in the sequence majeure partie 'most part'. In a second class, we still see a great preference for a given position but the alternating cases show less fixity. Two patterns appear within this class: the alternate order either corresponds to a use driven by one major constraint, or to a cumulation/interaction of different constraints. For the first pattern, the constraint involved is not necessarilly the same for every adjective. It can be semantically grounded, which usually leads to distinct nominal paradigms combining with the adjective given its position (e.g. ancien: 'ancien+N' means 'former', 'N+ancien' means 'old'), or it can be based on other devices, as illustrated by different. The data of the ER corpus differs from the FTB by the fact that it shows a strong preference for anteposition. The findings concerning the definite/indefinite nature of the NP were however confirmed, with 97,5% cases of definite in anteposition and 96% of indefinite in postposition. The adjective nouveau 'new' illustrates the second pattern: it prefers anteposition, but postposition is favoured when combined with a concrete noun, or ehanced when the NP is complement of a preposition. The third class concerns adjectives for which the general pattern shows a much weaker preference, if any, for one position over the other. There are however differences in usage for each position. The two patterns outlined for the preceeding class may also apply here: for instance, the placement of principal 'main' depends on a cumulation of information based on different grounds, whereas the semantics of pauvre (pitiful + N/N + not rich) clearly separates the uses. To sum up, the problem of adjective alternation does not depend on general principles, it is tightly linked to the item and to the NP within which it appears. Our study shows that the constraints previously proposed play a role in the placement of adjectives, but on a more specific level than the broad NP. In other words, locutors speak according to more specific patterns present in their linguistic knowledge.