diff --git a/internal/client/client.go b/internal/client/client.go
index 62954b5..f3c826c 100644
--- a/internal/client/client.go
+++ b/internal/client/client.go
@@ -66,7 +66,14 @@ func (c *Client) CreateShare(ctx context.Context, key string) (*types.Share, err
 		Key:  key,
 	}
 
-	// TODO: check if key exists
+	exists, err := c.s3.KeyExists(ctx, key)
+	if err != nil {
+		return nil, err
+	}
+
+	if !exists {
+		return nil, errors.New("key does not exist")
+	}
 
 	err = c.db.CreateShare(ctx, share)
 	if err != nil {
diff --git a/internal/s3/minio.go b/internal/s3/minio.go
index 0c80718..323008c 100644
--- a/internal/s3/minio.go
+++ b/internal/s3/minio.go
@@ -39,3 +39,18 @@ func (m *minioClient) GetObject(ctx context.Context, key string) (ObjectReader,
 
 	return object, nil
 }
+
+func (m *minioClient) KeyExists(ctx context.Context, key string) (bool, error) {
+	_, err := m.client.StatObject(ctx, m.bucket, key, minio.GetObjectOptions{})
+	if err != nil {
+		errResponse := minio.ToErrorResponse(err)
+
+		if errResponse.Code == "NoSuchKey" {
+			return false, nil
+		}
+
+		return false, err
+	}
+
+	return true, nil
+}
diff --git a/internal/s3/s3.go b/internal/s3/s3.go
index 8da9a9f..c59a67f 100644
--- a/internal/s3/s3.go
+++ b/internal/s3/s3.go
@@ -14,4 +14,5 @@ type ObjectReader interface {
 
 type S3 interface {
 	GetObject(ctx context.Context, key string) (ObjectReader, error)
+	KeyExists(ctx context.Context, key string) (bool, error)
 }