Let \(\mathcal{P}(n)\) be the set of partitions of the positive integer \(n\). For \(α=(α_1,...,α_t) \in \mathcal{P}(n)\) define the diagonal sequence \(δ(α)=(d_k(α))_{k \geq 1}\) via \( d_k(α) = \big\lvert \{ i \, \rvert \, 1 \leq i \leq k \mbox{ and } α_i + i- 1\geq k \} \big\rvert.\) We show that the set of all partitions in \(\mathcal{P}(n)\) with the same diagonal sequence is a partially ordered set under majorization with unique maximal and minimal elements and we give an explicit formula for the number of partitions with the same diagonal sequence.