Abstract. For a graph G = (V, E) the minimum line-distortion problem asks for the minimum k such that there is a mapping f of the vertices into points of the line such that for each pair of vertices x, y the distance on the line |f (x) − f (y)| can be bounded by the term dG(x, y) ≤ |f (x) − f (y)| ≤ k dG(x, y), where dG(x, y) is the distance in the graph. The minimum bandwidth problem minimizes the term maxuv∈E |f (u) − f (v)|, where f is a mapping of the vertices of G into the integers {1, . . . , n}. We investigate the minimum line-distortion and the minimum bandwidth problems on unweighted graphs and their relations with the minimum length of a Robertson-Seymour's path-decomposition. The length of a path-decomposition of a graph is the largest diameter of a bag in the decomposition. The path-length of a graph is the minimum length over all its path-decompositions. In particular, we show:-if a graph G can be embedded into the line with distortion k, then G admits a Robertson-Seymour's path-decomposition with bags of diameter at most k in G; -for every class of graphs with path-length bounded by a constant, there exist an efficient constantfactor approximation algorithm for the minimum line-distortion problem and an efficient constantfactor approximation algorithm for the minimum bandwidth problem; -there is an efficient 2-approximation algorithm for computing the path-length of an arbitrary graph; -AT-free graphs and some intersection families of graphs have path-length at most 2; -for AT-free graphs, there exist a linear time 8-approximation algorithm for the minimum linedistortion problem and a linear time 4-approximation algorithm for the minimum bandwidth problem.