We study the maximum size of Sidon sets in unions of integers intervals. If A ⊂ N is the union of two intervals and if |A| = n (where |A| denotes the cardinality of A), we prove that A contains a Sidon set of size at least 0, 8444 √ n. On the other hand, by using the small differences technique, we establish a bound of the maximum size of Sidon sets in the union of k intervals.